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GeneralLake Superior type agates from Lower Michigan
If you have a Lake Superior type agate found in the lower peninsula of Michigan please post it here. Unlike the multitude of Lake Superior agates found in the alluvial river gravels of the Mississippi River valley, agates of this type are exceedingly rare in the glacial till of Lower Michigan. I would like to plot the location of agates of this type on the map. I know of only two. The one that I have posted below from the gravel in the Au Sable River and another 6.5 lb. banded agate found on the Lake Michigan beach between Leland and Glen Arbor.
25th Nov 2014 14:17 GMTLarry Maltby Expert
The possible source for these agates is Michipicoten Island or Mamainse Point or, perhaps flow tops under Lake Superior between these locations. Please include agates from these localities if you have them.
This photo of the agate from the gravel in the Au Sable River was sent to me by a friend and I don’t have the size. I would guess about 2 or 3 cm. It is especially interesting because of the calcite casts outlined with agate banding.
We recently received a float copper from a gravel pit in lower Michigan. I'm not aware of any agates, but will look.
25th Nov 2014 16:16 GMTChris Stefano Expert
Chris, thanks for the info on the float copper from Lower Michigan. That is another rare find. In general, it seems that the flow of ice over the Great Lakes area was from northeast to southwest making Mamainse Point a candidate for the source.
25th Nov 2014 21:17 GMTLarry Maltby Expert
We will try to make it up there in the spring and I will E-mail you. Hopefully we can get together and I can get a picture of the float.
25th Nov 2014 22:38 GMTPaul Brandes Manager
As you already stated, the ice flows that covered/created the Great Lakes kind of came from the wrong directions to get agates or float from the UP down to the Lower, although in nature anything is possible. I suspect Mamainse would be a prime candidate, as would Michipicoten or Caribou Is. if in fact a "renegade" ice flow came from that particular direction. I don't believe I have anything from the Lower, but will have a look.
Looking at the photo you posted, I guess I should have been looking for agates in the gravels on the Au Sable in addition to fly fishing for brookies!! :-D
Yes Paul, I also have spent many hours wading the Au Sable fooling around with trout when I should have been looking at the gravel.
26th Nov 2014 13:26 GMTLarry Maltby Expert
The first mineral specimen I ever collected and retained was a perfect red and white concentricly banded Lake Superior agate. It is about the size of a walnut with a pitted vesicle wall cast texture on the exterior, and broken exactly along the center line of the agate. It was collected in 1958 and found because it was facing straight up with its interior perfectly displayed in a roadbed leading away from a gravel pit near Chilson, Michigan. I was keeping my eyes peeled, as my dad would say, for fossils, but this thing stopped me in my tracks. Chilson is about 40 miles NW of Detroit and near the larger town of Brighton.
1st Dec 2014 10:10 GMTBart Cannon Expert
I have an old 35 mm slide of my mom sleeping on a big erratic in the Middle of the Au Sable River. More of a long lake than a river as I have come to know them now, here in my Washington State habitat.
1st Dec 2014 17:01 GMTLarry Maltby Expert
Great to hear from you! I now have another data point for my study. About 4 or 5 years ago, I spent a lot of time studying the glaciation of Lower Michigan. As you know the “reworking” of the face of the earth by ice is a fascinating story. I live on the side of the Port Huron Terminal Moraine about 100 ft. above the valley floor. With all of the time that I have searched the till, I have never found a rock from the Keweenawan formation to the north. I do find “pudding stones” that can be traced to Bruce Mines, Ontario and many granites that are likely from the Canadian Shield.
The story about your first mineral specimen is similar to mine. I also was infected with the “collecting gene” but my focus was on biological specimens. I became disappointed because my pressed leaf collection was crumbling and the legs were falling off of my insect collection. Around 1950 we took a family vacation camping in the Keweenaw. There was no Mackinaw Bridge so we crossed the Straights on the car ferry. The famous Quincy No. 6 shaft house was still standing (burned in 1956). Huge poor rock piles were everywhere (now depleted by crushing for construction). I saw my first agates in local shops and was told that they could be found on the beaches. That was it! I would be a mineral collector. My collections would last forever! That was before my “cocks comb marcasite” from the tri-state area crumbled in its specimen box. Never-the-less, mineral collecting has stuck for a lifetime.
As a young boy of perhaps 10 years of age, I found a till agate in the city of Wyoming, Michigan (in southwest Michigan) in an area being excavated for a new car dealership. It did not have the coloration of a typical Lake Superior agate and I brought it to the local rock and mineral club several years later and some thought it was a Laker while others dismissed it as agate of undetermined variety. I no longer have the specimen but it was about the size of a plum with prominent banding but not of the right color for a Laker---it was more bluish and white with some iron coloration.
1st Dec 2014 17:45 GMTDana Slaughter
I began picking up rocks in the cornfields of Cass County, Michigan, and it sent me on my way to become a geologist. There were plenty of interesting things to occupy a young lad roaming the fields. Lots of crinoid stem pieces that we called "indian beads" and if you were really lucky a true arrowhead. Of course lots of granites and other assorted crystalline rocks from the shield. Of note, regarding ice direction, there were the occasional pieces of jasper pebble metaconglomerate (puddingstone) from the Bruce Mines area, and I once found a piece or rock that looks exactly like the Onaping Tuff from Sudbury area. Clearly, at least part of the deposition in Cass County was from the northeast, but I believe that there is a northerly component related to the Lake Michigan lobe in this area, and the Lake Michigan and Saginaw lobes were intermingling. I now live in the Lansing area, and puddingstones are common - this is full Saginaw Lobe material.
1st Dec 2014 19:04 GMTAllan Blaske
Regarding agates, I once found a yellow-brown (kind of butterscotch colored) agate that was clearly not a Lake Superior agate (I got a BS and MS at MTU so I know what the lake agates look like). However, I would occasionally find pieces of amygdaloidal basalt in the drift in Cass County, but they didn't look quite the same as stuff from the Keweenaw. Now in Eaton County I also occasionally find amygdaloidal basalt, but again the stuff looks too metamorphosed to be Keweenawan in age. There must be basaltic rocks with flow-top structures in the shield rocks that are older than Keweenawan, because I don't ever see anything that resembles the "fresh" basalts of the Keweenaw or the Mamainse Point area.
It would be interesting to take some of those amygdaloidal basalts you described Allan and try to do some geochemical fingerprinting of sorts on some likely candidates in eastern Ontario to see if anything matches up.
2nd Dec 2014 00:48 GMTPaul Brandes Manager
I had to chuckle at your one comment though Allan:
"I got a BS and MS at MTU so I know what the lake agates look like".
When I was going to school there (getting my MS as well), there were some MS and PhD students that thought they could tell you everything about a volcano by looking at a computer screen, but set a simple rock sample in front of them and they were completely lost; they had no clue what it was or how to ID it. Pretty sad........
2nd Dec 2014 22:46 GMTLarry Maltby Expert
If your agate showed banding then it is most likely from the basalt of the Lake Superior area and I will use the location where you found it as a data point. Over the years my son and I have extracted hundreds of agates directly out of the Lake Shore Traps in the Keweenaw and there is significant variety of color and form.
I also think that there was a north to south movement of the lobe in Lake Michigan. The shape of the lake suggests it. Also, during my research, I read a professional paper stating that after the ice front receded north past the Straights, there was another localized advance of the ice down Lake Michigan called the Valders Sub Stage (Greatlaken). The advance overrode the Upper Peninsula east of Munising and must have clearly been north to south. One wonders if some of the agates that occur on the beaches a Grand Marais were carried into Lake Michigan. If so, not many of them have been found!
It is interesting that you found amygdaloidal basalt in the till. As Bart says, I am going to keep my eyes peeled for that.
I had originally passed on commenting here because I figured my input was too anecdotal, but (1) I'm not the first on that front and (2) have to say hello to Allan B., one of my TAs when I was at Tech 1985-1989. (Hope you are well back in Michigan!)
3rd Dec 2014 02:28 GMTDon Windeler
I grew up in far SE Michigan in the town of Woodhaven, southern Wayne County. Circa 1980 I found a yellowish agate that sounds a lot like the one Al references; it didn't have the look of the traditional Laker, though I'll admit I'm no expert on the breed. I found it lying in the street, rather than in a quarry or other in situ locale.
Apropos of nothing, that's a piece I regret losing track of. There were rough vesicles on one side that looked like the scare mask from the "Scream" movie franchise, and I convinced my light-sleeping younger brother that it was a 'ghost vacuum' that would protect him at night. At some point he lost it -- not sure where or how, but now I wish I'd kept it and let him deal with his own concerns at the time!
20th Jul 2016 05:09 BSTJaimie Salzano
We live in northern Otsego county and find many wonderful agate specimens. Attached one of the better ones found in the woods.
Curious why agates only here because of glaciers and not volcanic activity? Michigan has 4 known volcanic periods, some of the agates/jasper specimens we've found look very similar to blue lace agates in Africa?
the glaciers came last is why ;-)
20th Jul 2016 11:14 BSTWayne Corwin
Definitely not a Lake Superior Agate Jaimie, and I'm not even sure what you have is an agate or just a frosted quartz nodule/chert. Still, in a land of sedimentary rocks and Petoskey stones, finding anything other than limestone is a real treat. Based on your location, your specimen is likely from Canada, brought to northern Lower Michigan during the last glacial maximum about 10,000 years ago. While it is true that Michigan has had several periods of volcanic activity in the past, the only notable activity in your neck of the woods was the Mid-Continent Rift which occurred some 1.1 billion years ago and is now buried deep under the Michigan Basin. The Michigan Basin is the reason you have so many oil/gas wells around you in Otsego County; they are into the Antrim Shale.
20th Jul 2016 12:13 BSTPaul Brandes Manager
5th Feb 2017 23:33 GMTJames Reitman
I'm interested in finding out more about this...From what I can find on the web it appears to be a blue lace agate (please correct me if I am wrong). The outer edges are covered in a very bright rust colored metallic material...Maybe iron? I found this a few years ago while working a landscaping project on Mackinac Island. I have lived on the island my whole life and have found many interesting things but never something like this. Also, i have never seen a possible source for the reddish color material anywhere on the island or surrounding area. It is a well known fact that Mackinac was a major hub for trade over the last few hundred years...Wondering if this was deposited here by glaciers or perhaps came by the hands of our ancestors. Any insight would be greatly appreciated!!
It is a pale blue agate for sure but not your typical "Lake Superior agate" which has red and brown bands.
6th Feb 2017 00:14 GMTReiner Mielke Expert
Hello all, I am new here but have lots to share. I believe this photo above is not from the U.P. It was in my opinion part of the Bois Blanc formation that makes up the bedrock in much of the tip of the mitt.
19th Aug 2019 02:53 BSTChris Leifson
The outer layer of red-brown is likely the ubiquitous iron oxide ("rust") which occurs pretty much everywhere. Hard to hide from it.
6th Feb 2017 00:35 GMTDoug Daniels
Larry, reading through your post reminded me of two areas in NE Iowa in which I collected a variety of agates and jaspers, one was the terminal moraine area in Chickisaw County golf course that was transected when the new golf course was developed about 15 years ago, and the other area was in the town of New Hampton, Iowa two blocks from my wife's family home where the excavations for a new housing development exposed some interesting lake superior agates when the foundations were dug and before the grass was planted this was about 8-9 years ago. Several family members who owned farming land would find small lakers in the local streams after spring rains flooded and scoured the streams and rivers of nearby fields.
6th Feb 2017 05:37 GMTSteven Kuitems Expert
Hope this would be of interest,
7th Feb 2017 11:51 GMTLarry Maltby Expert
Nice find from Mackinac Island. First of all, it is not necessary to try to name your agate with one of the hundreds of trade names that have been created by dealers that are selling agates. When a random agate is found in a location that is not known to produce a certain type of agate it is almost impossible to get agreement on what to call it other than just “agate”.
It is highly probable that your agate originated in the Keweenawan basalts to the north of Mackinac Island. The question is how did it get to the Island? The agate shows very sharp edges and a thin coating of iron oxides on the exterior surface. If it was deposited by glacial ice, the sharp edges would be rounded and the soft iron oxides would be worn off except in deeply pitted areas. As you suggested, it seems to me that the agate was probably extracted from the basalt by human hands and then lost on Mackinac Island where you found it.
Here is a link to a gallery of agates from Keweenawan rocks, many of them extracted from directly from the basalts.
Larry Maltby Wrote:
7th Feb 2017 12:07 GMTPaul Brandes Manager
>The question is how did it get to the
Post-glacial hominid activity, perhaps? :-D
And James: How lucky you are to live on such a beautiful island! (tu)
7th Feb 2017 12:41 GMTLarry Maltby Expert
It is interesting that you mention agates in the glacial deposits in Iowa. I can remember that when I started collecting in the 50’s and 60’s rockhounds were welcome to sit beside the conveyers in the gravel pits near Muscatine and pluck agates off the belts as they passed by. Those were the good old days.
perhaps a huge chunk of amygdaloidal basalt the size of a house could have been carried by a glacier. and dropped in places in lower Michigan creating whats seems like a source of agate. also how well explored are the bottoms of the great lakes. doesn't seem that unlikely that there would be some volcanic activity down there somewhere...
8th Feb 2017 22:26 GMTDaniel Bennett
the piece pictured above has all its edges so it either formed there(probly not), was put there by man (definitely possible)or was carried there inside a piece of basalt(either by glacier or water) and eroded on site. if that's the case the dirt where it was found (depending on the size of basalt)might resemble eroded basalt and differ from the normal sandy ground and another agate might be found in the immediate area. revisiting the landscaping site could help. otherwise yes a tourist left it there.
Daniel Bennett Wrote:
10th Feb 2017 01:32 GMTPaul Brandes Manager
> perhaps a huge chunk of amygdaloidal basalt the
> size of a house could have been carried by a
> glacier. and dropped in places in lower Michigan
> creating whats seems like a source of agate.
Perhaps, but in situations such as this, one would be wise to revisit Occam's razor and think about the simplest way an agate would have gotten to an island made entirely of sedimentary rocks such as Mackinac Island. As Larry suggested, I would venture to say it was extracted elsewhere, carried to the island by someone, then dropped/lost until found by James many years later.
Thursday, March 23, 2017
23rd Mar 2017 16:03 GMTLinda Fager
I stumbled unto your page because I was looking up more information on Lake Superior Agates and want to go to look for them one day soon.
I've never been to Lake Superior before- but, have visited the Upper Peninsula.
I found an Agate years ago at age 13 and knew it was an Agate but, no idea that it could be a Lake Superior Agate but, I'm sure
it is by your description and from what I've seen from pictures online.
I didn't even know they were valuable- I just have always been a rock hound and collected rocks even as a child because
Rocks fascinate me!
I DO still have my Agate and will send a pic as soon as I locate the bin I stored it in as we just moved a year ago.
Here's some details about it:
Found in Lower Michigan - at Birch Lake, Porter Twp., Cass County, Vandalia, MI in 1973.
I was 13 then and am 56 yrs. old today so, 43 years I've kept my Agate and have NEVER found another like it.
It was near the shore and I was just picking thru the rocks and found this one and my first quartz geode.
It is about the size of a 50 cent piece from what I remember but, I will send pics as soon as I locate it.
The bands are red, brown and yellow and resembles an eye.
I NEVER polished it- just loved it and it is the prettiest rock I own.
I like Petoskey rocks and they remind me of little spider webs and have a few of those.
But, don't think I have any more Agates- only this one!
I'm anxious to find it to show it off to you so, you can log the location of the glacier movement.
I'll be in touch soon.
the one to the left of the coin in the last two photos looks like a fossil coral colony
25th Mar 2017 12:15 GMTjeff yadunno
like this image i found:
i have found ones like the one above(not my photo) on the shores of lake ontario and georgian bay
Linda, great finds. Beautiful colored banded one is a score. I have a question for you, in your second picture with the coin: top left stone. I am trying to identify whtat the purple reddish part of the stone. It is located on the bottom section of the stone?
25th Mar 2017 22:34 GMTMichael Harwell
In picture 1 that you posted I believe the top right larger stone that is purpley reddish with some white material. I'm thinking these are similar.
I find them in California beaches as well. Always wanted to know what it is specifically.
Anyone? Any ideas?
Can you find Carnillian there as well? What would raw carnillian found on a sandy / pebble beach look like?
25th Mar 2017 22:55 GMTLinda Fager
Yes the one on the left I called a honeycomb rock- I found it in the same lake as my Agate-
I wondered if it could be of the Lake Superior Agate collection as same exact colors - I'm sure I found them the same day in lower Michigan- Cass County
But, I was hoping Larry- could identify my Agate as a Lake Superior Agate found in lower Michigan was the main reason I posted.
I have been a rock hound for years- but, a novice at minerals and Agates.
I have several other rocks found in Cass Cty., Lower Michigan that look somewhat like a beehive-
Thanks for sharing your fossils- those are too cool :)
25th Mar 2017 23:23 GMTLinda Fager
I have no idea what that stone is- I found all these in Lower Southwest Michigan, Cass County.
The banded one is definitely an Agate- the only Agate I own.
These are just some of my favorite stones I collected over the last 40 years- I have lots and lots more.
I put them in water in the white container to show the colors more.
I know most common stones- but, of course would like to know what this is too-
Thanks for your inquiry- maybe someone more advanced in rocks and minerals will answer our question :)
Yes Linda, your banded agate is a Lake Superior Agate. It most likely formed in a vesicle (cavity) in the Keweenawan basalts east of Keweenaw Point that are now covered by the waters of Lake Superior. That is based on the probable direction of glacial ice flow that would have carried the agate to your location. I have found agates similar to yours on the Lake Superior beaches in Keweenaw Co. and my son and I have extracted similar ones directly from the basalt of the Lake Shore traps west of Copper harbor. (see below)
26th Mar 2017 00:13 GMTLarry Maltby Expert
I have also found a few samples of agatized coral similar to yours on the beaches of Lake Superior however; I don’t know where they originated. The corals would not have grown in the igneous basalt.
26th Mar 2017 04:10 BSTPaul Brandes Manager
I would venture to say that your LS Agate is from the basalts on the east end of Lake Superior. Larry is correct in that it was the glaciers that brought your agate down to Lower Michigan. I too have found agates similar to Larry's on the beaches west of Copper Harbor. Many are gemmy, but some are also opaque and polish up quite nicely. The fossils found along Lake Superior are said to come from further north along Hudson Bay and brought south by the glaciers. Yours Linda could very well be from a local source as you are in the heart of the Michigan Basin.
Thanks Paul and Larry for the information.
27th Mar 2017 19:17 BSTLinda Fager
You said in an earlier post...
If you have a Lake Superior type agate found in the lower peninsula of Michigan please post it here. Unlike the multitude of Lake Superior agates found in the alluvial river gravels of the Mississippi River valley, agates of this type are exceedingly rare in the glacial till of Lower Michigan. I would like to plot the location of agates of this type on the map. I know of only two.
If My Agate is the 3rd Lake Superior Agate - that you know of- and exceedingly rare- then, do you know what it would be valued at?
I see online that people are selling Lake Superior Agates $300 and up - but, I do NOT wish to sell- just curious of it's value.
And I did not know the similar colored stone is a Lake Superior Agatized Coral- I just called it my Honeycomb rock!
Is that valuable as well? I forgot I had that one!
I have been a rock hound since a child but, admit I have not gone "rock-hunting" anywhere not even Lake Superior-
My rocks were just stored in bags but, now I've bought clear boxes to sort according to type and will make notes if I remember the location
I found them.
I collect all kinds- and really only familiar with common names- and I'm a novice to minerals such as Agates!
We are planning a day away in June and I was googling for more information on Lake Superior Agates because of an Article I had on the Agates from years ago and thought it would be neat to go rock collecting one day.
It's exciting to know I Own a Lake Superior Agate and Agatized Coral- as I found them both in the same lake and the geode next to them.
I found them only about 10 miles North of the Indiana Michigan State Line in Lower Southwest Michigan.
So, All my rocks have been found in Cass County, MI for the exception of a few I found on Trips visiting friends over the years and on walks.
I'm googling now for places to hunt the Lake Superior Agates- We may not have to go All the way to Lake Superior as some are finding them in Lake Michigan I read.
If you can suggest a good hunting spot or town, please let me know.
Larry, now you can record your 3rd point of Agates on your map :)
If you need more pics- please let me know.
I put my rocks in water to show the Agate bands better- but, read where some use mineral oil to coat and clean them.
Thanks again for All the information you have really enlightened my knowledge :)
I will continue to follow this thread and share other rocks of interest to you if I have any you want to see.
28th Mar 2017 03:53 BSTPaul Brandes Manager
If you can get away in August and travel to the Keweenaw Peninsula, you might be interested in registering for and attending the Keweenaw Week 2017 festivities, put on by the Copper Country Rock & Mineral Club August 7-11, and then the Annual Rock & Mineral Show August 11-13.
28th Mar 2017 11:56 BSTLinda Fager
Thanks for the information!
I'll check into it-
We can go any time but, just wanted a day get away to get back to our animals :)
But, I'm sure lots of good information here.
28th Mar 2017 15:00 BSTLarry Maltby Expert
I am the worst person of all to comment on the value of a specimen. I no longer think about the dollar value of what I collect or study. I am interested in your agate because of where it was found. You are interested in your agate because you found it yourself a long time ago. I don’t think that because your agate was found in an unusual location it adds much to the value. It is a very nice sample of a Lake Superior agate and I will plot its location on the map of Michigan. To put this in perspective, I am now 80 years old and I have lived all of my life in Michigan. I was an outdoorsman. I have hunted, fished, hiked, collected in streams, beaches, and gravel pits in the Lower Peninsula and I have never found a Lake Superior agate there. You found a very nice specimen.
If you are going to collect on Lake Michigan beaches I suggest that you look for a “free stone” beach. A “free stone” beach usually has a sandy substrate and if there is gravel present, it will be washing in the waves at the waterline. During storms the gravel and sand will tumble and that action will keep the rocks clean. If the substrate is clay or marl, the gravel will be “impacted” and will not tumble. It will become coated with algae, etc. and you will not be able to see the color and texture of the rocks.
28th Mar 2017 15:58 BSTTimothy Greenland
How nice to see the term "impacted" used in its real sense rather that the modern abuse of 'having an impact on' !
28th Mar 2017 16:23 BSTLarry Maltby Expert
That term goes back to my trout fishing days. Trout streams are either free stone or impacted. Free stone is better because it provides better habitat for aquatic insects (trout food). It also aids in spawning (more fish). And, when you think about it, it helps beach collectors too.
Another common point! I used to enjoy trout fishing on the Welsh border in my youth. We had a small stream (not impacted) with purely wild river trout on the farm I frequented. They fed on all sorts of wild insects and, when big enough, crayfish. They were delicious!!! I used to tie my own flies to imitate the local insects... When I last passed through the region the stream was severely degraded - though not yet ruined... Keeping my fingers crossed that there will still be fish there for my descendants...
28th Mar 2017 17:20 BSTTimothy Greenland
PS I must stop hacking this thread - I have no knowledge of Lake Superior agates, so my musings are to be ignored.
thank you Larry for the term Freestone to describe the beach, I wondered if it had a name. I see you put it in quotes So maybe it's not an official designation but thanks just the same.
28th Mar 2017 17:22 BSTD Mike Reinke
29th Mar 2017 13:44 BSTLinda Fager
I appreciate all your input and I'm glad I found this forum to post about my LS Agate and Coral.
I have learned alot and finding more information online.
Thanks to everyone who have replied to give me their input.
It is greatly appreciated.
If there are other rocks of interest that you seek from lower Michigan- please let me know....I may have one!
Sorting my rocks last night I found a Quartz with actual clusters of Crystals sticking out of it and I can only remember that it was
left at a Farmhouse we purchased and lived at for 16 years.
I Did not find this rock. I didn't write a note where I received it from but, it wasn't in the bag of special rocks I had found-
So, I'm sure it was from the farmhouse and the owners left a small old rock tumbler and I knew they
travelled so, I'm guessing this came from Out West somewhere.
It was exciting to find it among my collection for sure.
I'm starting to organize all the rocks I've found- and I'm surprised and fascinated by them all :)
If you need pics of anything I'll be happy to oblige-
Thanks again for the type of shores I need to look for since I've never been in the UP to rock hunt- but, just
once or twice to a cabin for a get away.
My email: email@example.com
If you feel you need to contact me for anything :)
Paul Brandes do you have any photos of your 'gemmy' lake superior agates-
14th Apr 2017 10:52 BSTLinda Fager
I found this online- it's gorgeous.
Is yours like this one?
Would love to see what yours look like also.
Trying to verify what types of agates I have found recently on a southern Lake Michigan beach. Always find petoskey stones and fossilized coral, but this year I have been finding these. Any information would be helpful, glad to add them to my collection.
1st Aug 2017 03:00 BSTWilliam W
William, this is also bois blanc formation. If I had to say those came from 9 mile point in Emmet county.
19th Aug 2019 02:57 BSTChris Leifson
Very nice. I'd love to see more. I'll let the experts identify.
1st Aug 2017 03:37 BSTMichael Harwell
They certainly look like agates, with the second pic looking like a Laker.
20th Aug 2017 03:00 BSTPaul Brandes Manager
All three are very nice!
Hi my name is kim i live in northwest lower peninsula on lake Michigan in manistee michigan. I have been seriously rockhounding for 16 yrs but have always picked rocks since i was little . Out of 16 yrs i never found a lake superior agate in lake Michigan UNTIL this year. I found 2 ♡♡ both are very waterwashed (smoothed ) one is a psdomorph and the other a true floater (banding with quartz center with another center of banding in the quartz). I was posting because u seem interested in where they are found in lower mich.
22nd Nov 2017 05:47 GMTKim (Kim Agrusa)
Thanks for the information Kim,
22nd Nov 2017 11:51 GMTLarry Maltby Expert
I have collected the Lake Michigan beaches north and south of Norwood, Michigan but have never found a Lake Superior type agate. The beaches are covered with a great variety of interesting rock materials from further north and provide some interesting collecting. I am currently working on other projects but I do plan to plot all of the location data here on the map of Michigan. Eventually I will post it here.
The material on this beach is Norwood banded chert. I have also found Bois Blanc formation here.
19th Aug 2019 02:57 BSTChris Leifson
Welcome to Mindat, Kim!
22nd Nov 2017 23:34 GMTPaul Brandes Manager
Thank you for this information. If possible, could you please post a photo of each for us to see?
23rd Nov 2017 03:40 GMTBill Baker Barr
Back in the 1950s and 60s when I was a kid, I probably looked at every beach pebble at the north end of Mullett Lake in Cheboygan County at the tip of the mitt. Among many other treasures, I found one small agate that I am pretty sure was a Laker. It was about 2 cm across, beach or ice worn but with one broken surface, with tight, contrasty red and white banding. It may still be squirreled away somewhere up at the cottage. The beach where I found it is at the very northernmost point on the Mullett Lake shore, about 1/4 mile west of the Cheboygan River.
Other finds there included non-Laker agates, some seemingly nodular but many more as veins in sedimentary rocks; a partial trilobite impression in a marly-looking sediment; and agatized corals, which were fairly common (until I picked them all up). I also found one small piece of what the Canadians call peristerite with a beautiful blue flash of adularescence.
Down in the southeast corner of Michigan, we find a pink, white and gray agate, kind of porous with some oolitic structure (see photo). It's kind of pretty and takes a polish if you can work around the little drusy crystal pockets. It occurs in glacial gravels, and I guess its bedrock exposure could be somewhere under Lake Huron or up in Ontario near Bruce Mines, where the puddingstones come from. It might be nice to track its source down. Canadian brothers and sisters, do any of you recognize it?
Agates... gotta love 'em!
If anyone has more information on Michigan Oolitic Agates, like the photo just posted by Bill, please let us know, especially as to the pre-glacial origin. I live on a large glacial moraine next to gravel pits outside of Brighton, Michigan and we find these in our yard. In fact, I found one this morning raking leaves. It is softball size with good pink color. It is now soaking in bleach to remove organic material. As soon as it cleans up, a picture will be posted. I have also found these in Pinckney Recreation area near Hell (about 20 miles to the west and 10 miles to the south). They were again found on moraines. On occasion. some of these agates have sections with fossilized colony coral.
23rd Nov 2017 05:00 GMTWalter Kellogg
Hi Bill and Walt,
23rd Nov 2017 11:26 GMTLarry Maltby Expert
Thanks for the info. I had forgotten about this oolitic cream and red agate found in the till in southern Michigan. I do recall that an article was written about it in the pre “web” days. The article was in one of the magazines, perhaps an old Lapidary Journal when it still had a mineral collector focus. I have since given all of my old mags to my son. It would take hours to find the article. Maybe someone will come across it and report it here.
I do not recall that the in-situ location of this material is known. As Bill pointed out the in-situ location of the pudding stones is near Bruce Mines. It would be interesting to start a thread about what is found in the till of the lower peninsula of Michigan.
Happy Thanksgiving Bill and Larry:
24th Nov 2017 01:43 GMTWalter Kellogg
I agree, perhaps we should start such a thread. Over the years,people have shown me a number of specimens of amethyst they had found in southern Michigan. On at least two occasions, it was attached to red granite and sure looked like Thunder Bay material. Also, I was told there was a large boulder of the same material, red granite and all, the size of a small car, located between Brighton and Pinckney. The point being, the Keweenaw is in almost a direct line between Thunder Bay and SE Michigan. So, it certainly is possible a few lakers made their way down here.
Still waiting for the oolitic agate to clean up to get a picture. I hike a lot in Pinckney, Waterloo and Island Lake Rec. areas (almost daily) and always keep my eye on the ground. Lots of chert, ocher colored jasper, pudding stones and an occasional oolitic agate - but never anything looked like a laker agate (or amethyst for that matter).
24th Nov 2017 23:47 GMTPaul Brandes Manager
There seems to be a reference to Michigan oolitic agate in Lapidary Journal, v. 12, no. 6, p. 805.
Walter Kellogg Wrote:
25th Nov 2017 01:55 GMTPaul Brandes Manager
> The point being,
> the Keweenaw is in almost a direct line between
> Thunder Bay and SE Michigan. So, it certainly is
> possible a few lakers made their way down here.
Not a chance! Think about the direction of the glacial lobes as they moved out of Canada. The lobes that moved over the Keweenaw dropped their goodies into Wisconsin, Minnesota and points southwest. Most, if not all, of the material you're finding in the glacial tills of lower Michigan came from northern and eastern Ontario via the Lake Michigan, Saginaw, and Huron lobes. The Lake Michigan lobe likely brushed current eastern Lake Superior during the last glacial maximum which would have picked up material from those areas which are known to contain native copper and possibly, agates.
Concerning the oolitic agates, I would bet these are coming from areas like Bruce Mines, Blind River, and points north.
Paul et al,
28th Nov 2017 02:04 GMTBill Baker Barr
Seems like there would have been a LOT of water flowing in all directions when those glaciers started to melt. Isn't it possible that some of that rushing water carried material from the Lake Superior agate beds toward what became the Lower Peninsula, either directly or by moving material that had already been dragged southwest by the ice?
As for the oolitic agate, I'm hoping to take a trip next year (after this winter's glaciers melt!) to the north end of Lake Huron, looking for puddingstones and minerals. I'll keep my eyes open for oolites.
I'm on the Illinois side of Lake Michigan. Never found a Laker here but we have plenty of agates called Lake Michigan Cloud Agates according to the Gitche Gumee museum. They are cold water agates with decent structure and translucency formed in limestone and dolostone within the Niagara escarpment.
19th Apr 2018 15:07 BSTLars ADAMS
I can see that I have missed several posts in this thread.
19th Apr 2018 17:10 BSTLarry Maltby Expert
Walt, I agree with Paul. The evidence is strong that the “Keweenaw” agates were pushed by the ice toward Duluth. I have a friend in Copper Harbor that has done a lot of scuba diving looking for agates. He told me one day that there were glacial groves under Lake Superior in front of his house (about 4 miles west of Copper Harbor). I asked if they were parallel to the shore in an east to west direction. His answer was yes. Due to immense pressures, glacial ice becomes “plastic” and will divert direction when it encounters an obstruction like the Keweenawan Highlands. Compared to the huge amount of agates found in the alluvial gravels of the Mississippi River watershed, the number of agates found on Lake Michigan beaches and in the Lower Peninsula is very few. The ones that are found likely came from the area of Michipicoten Island.
Bill, as the ice melted the outwash is well documented over geological time. It is detailed and complicated. If you take the time to do the research it is an interesting story. The most prominent outwash was at the west end of Lake Superior into the Mississippi River watershed and, down the St. Lawrence River valley into the Atlantic Ocean.
Lars, your gray and white specimen looks like banded chert to me. I have seen this in the glacial till in several places.
22nd Apr 2018 00:50 BSTPaul Brandes Manager
If they are "cold water agates" formed in limestones/dolostones, they are likely banded cherts rather than true agates. I also note the sugary texture these appear to have, not indicative of an agate.
There is some problematic characteristics in these "cold water agate" or "cloud agates". First is the crystalline texture which, if macroscopic, means it falls into the quartz and not chalcedony (agate, chert, flint, etc) classification. The sugary texture also indicates a recrystallization possibly of earlier silicification of the parent sedimentary rock
22nd Apr 2018 02:23 BSTGregg Little
Secondly the laminations are unusual for agate in that they are not concentric or in parallel lines as seen in various nodular agates. Instead the layers are reminiscent of sedimentary structures like discontinuous, truncated, fore-set and top-set lamina. Theses characteristics may point toward a silica replacement of sediments or sedimentary rock, possibly a carbonate as indicated by Paul B.
In contrast to the "cloud agate" see the "oolitic agate" earlier in this thread which clearly appear as silicified fossil structures of a microcrystalline or cryptocrystalline grain size.
One further follow-up to my opinion of the cold water agate and its crystallinity is regarding the sequence of alteration. IF the recrystallization of the rock was initially calcite (forming marble) followed by silicification, replacement of calcite by microcrystalline quartz, then the rock could fall within the agate category. At this point microscopic work would be necessary to be definitive,
22nd Apr 2018 18:04 BSTGregg Little
I found a really nice agate on the shore mid way between Petoskey and Charlevoix. I've also found a really small agate somewhere on the shore south of Petsokey as well.
24th Apr 2018 04:10 BSTIain Brown
Pictures of them on my google plus.
29th Apr 2018 00:37 BSTGordon Grimm
In following your lead on locations of agates found,I found a blue banded agate,possibly a peeler,in an odd place.
I found this one on top of a glacial hill in Bellaire Michigan! I found smoky agates here and now a. Blue one!!!
29th Apr 2018 18:46 BSTGregg Little
I am always fascinated with the agate collector's terminology. What is your definition of a "peeler".
Both of these agates are originally from further north in Canada, brought down by the glaciers and deposited in the moraines and kames throughout the Lower Peninsula. All are nice examples....
29th Apr 2018 20:12 BSTPaul Brandes Manager
Gregg: a "peeler" agate is one that has been exposed to the elements over time and through differential weathering, some of the bands erode faster than others. The result is an agate that appears to have had its layers peeled back, almost like an onion.
29th Apr 2018 20:53 BSTLarry Maltby Expert
Thanks for the photos and the location. I am currently working on a project but when I finish I still plan to log all of these locations on a map of Michigan.
Here is a photo of a "peeler" that my son collected in the Lake Shore Traps in Keweenaw Co. Michigan.
Thanks Larry and Paul;
29th Apr 2018 21:58 BSTGregg Little
A novel name. Reminds me of exfoliation in granite but of course, a different weathering process.
I know of a few small thumbnail size LSA's found along lake Michigan shoreline just north of elk rapids and torch lakes east side,but never a blue tinted one, what would cause that color? just curious because most round here are a yellow tinted or a reddish tone with white.
30th Apr 2018 05:12 BSTGordon Grimm
30th Apr 2018 13:35 BSTLarry Maltby Expert
Agates are often composed by layers of chalcedony a microcrystalline form of quartz. The natural color of chalcedony is usually shades of white to gray and pale blue. The vivid colors in agates are thought to be caused by various impurities. The red colors that you mention are likely caused by microscopic inclusions of iron oxides. The color of the specimen that you posted here may be the result of the lack of impurities.
Thank you for the info!!
1st May 2018 04:13 BSTGordon Grimm
6th Aug 2018 23:40 BSTAdam Wolgamott
I found these 3 agates, the middle one was found in Lake Superior and the other two were found in Lake Michigan in Antrim county. I have some others from Lake Michigan as well but I chose to tumble them so I’ll have to share them with you in a few weeks.
Hey Larry, this one is not from LP of MI but it is from a SE WI lake Michigan beach. They seem to be very rare to find here as well is my understanding.
19th Dec 2018 23:33 GMTBrian Fussell
Again, likely carried by the same set of glaciers that flowed across what would become eastern Lake Superior and scoured out the basin that Lake Michigan occupies today.
20th Dec 2018 05:10 GMTPaul Brandes Manager
Beautiful agate, fuss!!!
Boardman River, Traverse City. Wading in the river(miles upstream of TC) when I noticed a patch of gravel that seemed out of place. It took me a sec, but I realized that this whole patch of rock was what you’d find walking along Superior, and I mean EXACTLY like walking on Superior beaches. Perplexed, I paused on my fishing, started picking up rocks, and found a few blanks, and then BAM! Just a-glowin in the sunshine was this guy. Cool little deposit or whatever it is.
9th Jul 2019 06:57 BSTDylan Prosch
Hi Larry, I am nee here but like you was searching for people who have found agates on lake Michigan or Huron. I have been studying the beaches here in the Tip of the Mitt for the last five years. In that time I have learned how to find agates on the daily at the right beaches. We are fortunate in the top to have a lot of glacial dump, and because of that I believe its possible to find many a carnelian laker, but more common to find yet less known is agates from the Bois Blanc formation. After learning about this formation, seeing it on Bois Blanc island, and then continuing to see it elsewhere in my area I have been able to examine many agate and psuedomorph agate specimens. Many of these have been posted on this page already as a blue/white/grey chalcedony in a limestone matrix. Oftentimes there is yellow or white calcite in the centers rather than quartz. Predominantly these agates are from fossils that were replaced with agate material, or agatized fossils. Some of my favorites are brachiopods that have agatized centers, and once all the shell is eroded off it leaves a beautifully designed agate in the center, kinda like a pearl. Within this matrix it is also possible to find pure chalcedony agates formed in a vesicle rather than a fossil. This reminds me of what was found on Mackinac Island in the pics above. Interestingly, iron is persistent here and if enough of it gets into the pure blue/white chalcedony it creates yellow to red bands. I recently found and agatized fossil that has pyrite in it. I would teally like to discuss this topic more, and I encourage everyone to check out Bois Blanc Formation... i will post some agate pics.
19th Aug 2019 03:12 BSTChris Leifson
Please excuse the typos... so in this picture you can see agatized horn corals and favosite fossils in the center. Left bottom is brachiopod agates... bottom right some of the carnelian agates and some brecciated agates. Top center is a beautiful banded sard agates, agates are in the bands and each band is a different color from yellow/brown, red/pink/orange, bue/ lavender/, black/white. Top right is a favosite where each cell has a different agate. All the blue whit yellow fossils are Bois Blanc formation.
19th Aug 2019 03:43 BSTChris Leifson
Brecciated fossil agate with more agate than fossil
19th Aug 2019 03:50 BSTChris Leifson
Agatized brachiopods with iron stains
19th Aug 2019 03:51 BSTChris Leifson
The backsides that highlight the shape of the shell
19th Aug 2019 03:52 BSTChris Leifson
Agatized fossils more bois blanc formation, notice the blue/white formation caused by the crystallization of pure limestone
19th Aug 2019 03:53 BSTChris Leifson
Beautiful banded sard agates. I have only found these at one beach.
19th Aug 2019 03:54 BSTChris Leifson
Super rare agatized favosite. I should add the Bois blanc formation is onondaga limestone the has fossils dating back 400 million years old.
19th Aug 2019 03:55 BSTChris Leifson
Carnelian agates with a couple oddball green agates all from Emmet county
19th Aug 2019 03:58 BSTChris Leifson
19th Aug 2019 04:00 BSTChris Leifson
20th Aug 2019 01:58 BSTLarry Maltby Expert
Thanks for the photos. I think that you have had better luck than most in finding agates in the Lower Peninsula. The photo second from the bottom shows very nice Lake Superior Agates and just above that is an exceptional fossil replacement with great color. Your post is a valuable addition to this thread.
Currently I am working on another subject but I will eventually return to this thread and will map all of the locations given here. There are more finds of Lake Superior Agates in the Lower Peninsula than I thought when we started this thread.
20th Aug 2019 02:55 BSTPaul Brandes Manager
Welcome to Mindat, Chris!
Some great finds you have there, especially the Lakers from Emmet County. However, I'm not entirely convinced that what you're calling agates are actually that, but rather multicolored banded cherts. It's not unusual to find chert in limestone, and the Bois Blanc seems to have an abundance of chert and fossil fragments being replaced by chert/quartz. Don't get me wrong, some of those are indeed agates (and very nice ones at that). Agree that Photo 994273 is an amazing specimen.....
Those banded cherts are translucent and have fortification agates in the different colored layers. I call them sard agates as they are predominantly yellow chalcedony with different colored bands and tiny seam agates. they are definitely not Lake Superior agates but do fall under the definition of agates in general. They are too beautiful and at times enough fortifications that I call them agates roughly.
22nd Aug 2019 00:01 BSTChris Leifson
Paul, this brings up an interesting question which perhaps will help others and ourselves. Ultimately, how do you define an agate, as the scientific definition is translucent and banded form of microcrystalline quartz. Obviously that is broad, and inclusive of many formations. But take for instance agatized fossils... are they agates? Perhaps not as the vesicles the agates formed in are fossil and many of the bandings are a resilt of the fossil shape. However... in the case of the brecciated fossil agates shown above maybe more agate as there is more botryoidal chalcedony than fossil. Onyx is another agate formation where the banding is concentric, but the banding can be multicolred. Ultimately, onyx was a word that artist used to describe banded chalcedony that could be carved to show contrast because of their color, Onyx=agate. This is also reflected in the fact that beyond fortification agates many agates like moss, whorl, jaspa water-line, and stalactite agates (to name a few) do not generally have as defined lines as fortification agate, but are definitely banded chalcedony. Many of the agates I have are calcite based rather than quartz. This is identified by the pink to green/yellow fluorescence under UV light. Maybe this takes them out of the agate definition?. From my perspective it is the quality of color and banding that make a chalcedony an agate regardless of the formation type. Also, be it UP or LP these other formations will likely be more common to find. It would be great to hear your input, and how you define your agates.
22nd Aug 2019 01:37 BSTChris Leifson
This is the same yellow formation
22nd Aug 2019 01:39 BSTChris Leifson
The amount of different colors in this formation combined with the bands and translucency lends me to call them agates.
22nd Aug 2019 01:41 BSTChris Leifson
CHRIS, Sorry, but I take issue with your calling a calcite with banding patterns or fluorescence "an agate". Look up any standard dictionary definition, geological or otherwise, of "agate" and you will find that the discussion is only of microcrystalline quartz. Nothing is mentioned about calcite or, for that matter, any other mineral such as banded fluorite (blue john etc) or baryte with growth bands. By your definition even this fluorite or baryte with a banding pattern or fluorescence would be an agate which just is not true.
22nd Aug 2019 02:21 BSTBob Harman
Agate, by all definitions is microcrystalline QUARTZ with banding or lacy patterns.
22nd Aug 2019 13:57 BSTLarry Maltby Expert
Bob, I don't think that Chris said that calcite was agate unless you are referring to the statement "Onyx=agate." That statement is true. You may be thinking that the word "onyx" is Mexican calcite but that is a marketing misnomer. I think that the abundant carvings from Mexico are actually travertine. The definition of onyx is: “translucent chalcedony in parallel layers of different colors. The first known use of the word onyx was in the 14 century in the meaning defined above."It was used historically by lapidaries to carve cameos, especially in black and white as seen here.
Larry, If you read Chris' last long paragraph, toward the end. His sentence beginning " Many of the agates I have are calcite based rather than quartz........" And reading on, Chris asks about how we feel about his definition of agate with a question mark.
22nd Aug 2019 14:11 BSTBob Harman
That is what I was referring to.
Bob, thanks for the clarification. I took the statement "calcite based rather than quartz" to mean that "agate like" material was found in a calcite environment or matrix. We do have some very unusual quartz and calcite fossil replacements on Lake Michigan beaches. I have found my box of specimens and am in the process of photographing. I will post soon. I have wanted to discuss this for a long time and this provides an opportunity.
22nd Aug 2019 15:33 BSTLarry Maltby Expert
This is a large favosite fossil replaced by calcite, however, the upper right portion of the specimen is replaced by quartz. The specimen is 11.0 cm wide and the silicified portion is 6.0 cm wide. The differential weathering clearly illustrates the quartz portion. It was found on a Lake Michigan beach in Antrim County. Many of these can be found in various patterns of calcite and quartz. I think that this is what Chris was referring to. The ambiguous terms of "agate" and "agatized" are plastered all over rock and mineral literature and often result in added discussion.
22nd Aug 2019 17:14 BSTLarry Maltby Expert
I have a friend who was a geologist for the State of Michigan and he told me that, in general, fossils from the Silurian are replaced by quartz and fossils from the Devonian are replaced by calcite. These specimens seem to have originally been replaced by calcite and then underwent a secondary replacement with quartz. I have not found a proposed geological event that would explain this.
LARRY, Like you I have many silicified fossils and silicified ("geodized") fossils, all from Indiana. Some were previously pictured in the Midwest geode thread. While most of these type geodes are solid, some are hollow with typical geode cavities lined by druzy quartz crystal tips.
22nd Aug 2019 18:32 BSTBob Harman
To me it is sort of a matter of semantics of how you want to define "an agate". But the narrow definition of it just being limited to microcrystalline quartz with banding or lacy patterns, is the definition I prefer. For any one to include other non-quartz minerals with banding patterns an agate or to include adjacent non-quartz formations in the agate definition, opens a pandora's box of unnecessary complications.
Consider this rather silly situation for considering other minerals with banding patterns as agates:
In 2011 I visited Alaska and saw the terminus of Mendenhall Glacier. The terminus was about 50' high. Ice, the crystalline form of water, is considered a mineral. At the glacier's terminus there were many many parallel bands of grayish debris and gravel etc. If ice is a mineral, would it be appropriate, with this broad definition of an agate of any banded mineral, to consider the terminus a large agate?? I think not...... Agate is just banded microcrystalline quartz. CHEERS.....BOB
Bob, I did not mean to infer that calcite is somehow agate and I don't think that Chris was inferring that either. Agate is a variety of chalcedony as is repeated over and over on Mindat. However, I don't think that the term agate applies only to "banded" chalcedony. I prefer the definition that is given on the Quartz Page written by Amir Akhavan.
23rd Aug 2019 01:34 BSTLarry Maltby Expert
"A chalcedony is usually called an agate if it exhibits any of the following properties:
Banding of whatever kind, caused by different colors or different structure of the layers, or both.
Translucency in conjunction with being multicolored.
Translucency in conjunction with a nodular shape and colored inclusions."
This allows for Moss Agate, Fire Agate, Plumb Agate, Dendritic Agate, etc. all without banding to be included in the definition.
By the way, Fossil agate is listed under Chalcedony on Mindat. It is defined as:
Fossil Agate - Agate as a replacement material in fossils.
I really appreciate you both getting in this discussion, and definitely wish I had more time to write this with ultimate clarity. Larry and Bob I agree with all that was said. Definitely and agate is translucent banded microcrystalline quartz and keeping to that definition is the goal. However, as we all stated that definition is oddly ambiguous itself. By that definition the yellow and colored banded chalcedony I posted above as odd as they are, remain agates. Furthering, the questions which Larry helped address is agatized fossils. I question if they are agates because the banding is often caused by the fossil structures rather than say a basalt vesicle. My conclusion being that if there is more agate than fossil perhaps that deserves agate status:). However... all this leads to the pink fluorescent agates I found, all here in Emmet County. Because of the material they were formed in and their location of discovery. I know these agates come from the Bois Blanc formation which makes up the bedrock in areas of the tip, particularly bois blanc island (reflecting on one of the above posts on this page from Mackinac island). Bois Blanc formation is Onondaga limestone that holds fossils from the Devonian. Larry really threw in some great information here as he mentioned a professor who said that would likely crystalize to calcite. Also, from what I know limestone (calcium carbonate) often crystalizes to calcite. With that being said. When I say calcite agate, I am referring to a chalcedony with bands that have calcite included, or that terminate with a calcite crystal rather than quartz. While it is hard to take an image of a stone under blacklight I did my best to highlight calcite fossils and their pink fluorescence, then took a comparative picture of the agates to give examples.
23rd Aug 2019 05:57 BSTChris Leifson
This is the blacklight photo of the same stones
23rd Aug 2019 06:04 BSTChris Leifson
Fluorescent calcite fossils
23rd Aug 2019 06:05 BSTChris Leifson
Same fossils without.
23rd Aug 2019 06:09 BSTChris Leifson
On a side note, I have found that many fossils can be easily found with a blacklight because of the calcite, and occasional agate or calcite crystal.
23rd Aug 2019 11:45 BSTLarry Maltby Expert
Here are two of your statements:
"....agate is translucent banded microcrystalline quartz and keeping to that definition is the goal."
"When I say calcite agate, I am referring to a chalcedony with bands that have calcite included...."
Your choice of words "calcite agate" is contradictory on its face. It is like waving a red flag in front of a charging bull. Using that combination of words will doom you to endless paragraphs trying to explain what you really mean. Your specimens in the last photo all look like calcite to me. You need to supply more evidence to make your point. Perhaps soak some of your specimens in acid or vinegar and see what is left or do a hardness test on each band.
You seem to want to force the word "agate" into your descriptions. It is not necessary.
The thing is that I am not really trying yo prove anything. I am just offering information about different types of agate formations. If an agate calcite is too contradictory I will just simply say, microcrystalline quartz banding with calcite inclusions. Kinda like calling an agate in a fossil a fossilized agate, or one with rutile a rutiliated agate, or jaspa-agate that has jasper. Just following the trends...
23rd Aug 2019 12:29 BSTChris Leifson
I definitely understand how it is a contrary statement, I just come from the perspective that when the word agate is used we are always discussing banded microcrystalline quartz. The descriptor added just denotes inclusions or formations within the banded microcrystalline. Certainly, I am not trying to redefine the word agate.
23rd Aug 2019 12:39 BSTChris Leifson
One thing I believe you're confusing here is that the term "agate" is not a descriptor for all banded rocks, it is the definite and reserved scientific name for a banded chalcedony (microcrystalline variety of quartz) that is translucent to semitransparent. So, when you say that you have a banded calcite, that's exactly what you have; it is not an "agate". As an aside, the term "jasper" is the scientific name for a chalcedony specimen that is opaque.
23rd Aug 2019 15:03 BSTPaul Brandes Manager
THANK YOU, PAUL!
23rd Aug 2019 16:26 BSTBob Harman
That was one of my important points from my above postings. Chris' postings have had some very ambiguous language. Agates can come from sedimentary, igneous or metamorphic environments, but the agates themselves are, as you noted, banded microcrystalline quartz/chalcedony and nothing else. CHEERS.....BOB
And I would like to clarify several other points.
23rd Aug 2019 16:48 BSTBob Harman
Agates can be discussed from 2 points of view. They can be discussed from a geologist's point of view or a collector's point of view. Overlap....yes, but different points of emphasis.
Agates can and do have inclusions (calcite???), but usually of resistant microminerals. From the collectors point of view, the presence of occasional inclusions are usually minimized as unimportant or just not mentioned.
Finally, experienced agate collectors look for whole agates, slabs or at least large pieces with nice architecture. Small agate pieces abound, but, except in a few circumstances, don't excite too much interest to experienced or advanced collectors. Many small pieces, as has been previously mentioned, are difficult to definitively identify.
Found this yesterday, again... banded chalcedony but in the following pic you can see that it has a big chunk of hematite, and iron inclusions. Hematite agate
24th Aug 2019 17:43 BSTChris Leifson
This section is magnetic
24th Aug 2019 17:44 BSTChris Leifson
I guess the answer as usual is right in my hands all along. This section from my Lake Superior Agates Field Guide ( Lynch & Lynch, 2012) quickly mentions that calcite can form in the same vesicles as agates and the chalcedony bands form around them and become inclusions. This is what I am trying to discuss about the Bois Blanc Formation agates and why some of the fluoresce.
24th Aug 2019 19:25 BSTChris Leifson
Check out the Thunder Bay Agate whose formation usually consists of some calcite.
29th Aug 2019 01:35 BSTChris Leifson
A report on the deposit from 2010 found the material from the Thunder Bay Agate Mine formed in cavities within the Fe-carbonate unit of the Gunflint Formation. It is suggested that the original ferroan dolomite was dissolved away, leaving cavities for later silica-rich fluids to form the agate as very delicate ringed stalactites and rarely stalagmites. There is no mention of calcite being involved in the formation of such agates or being found with the agates themselves. Typically, the agate from Thunder Bay is associated with white and sometimes reddish quartz crystals likely stained by iron from the Gunflint. That I know of, no TB agate has been found with calcite.
30th Aug 2019 20:13 BSTPaul Brandes Manager
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