Identity HelpUnknown from Rockport Quarry, Michigan
I collected this specimen on a collecting trip I took with my father near the end of October. We visited many of the quarries near Alpena, Michigan, including the one at Rockport. We went there mostly to collect fossils, but stumbled upon this rock. My original thoughts were that this was just calcite with dolomite, but the strange shape of some of the crystals has me confused. For example, some of them seem tabular in shape, which has me thinking celestine aswell. I collected other specimens that were obviously calcite because of their shape, but these just don't seem to fit for calcite. This has been bothering me since I collected it, so I figured I get some more experienced input on this. Also, the crystals seem to have a dusting of another mineral covering them, which to me seems like pyrite or chalocpyrite. Thanks!
Taylor,
Looks like calcite, and possibly dolomite. There looks to be some scalenohedral calcite crystals in the first picture. One way to check is to try an acid test. Break a piece off and drop it in some type of dilute acid (HCl commonly sold as muriatic acid for pools, CLR cleaner, or even vinegar should do), and it should fizz. When using an type of acidic substance, please be careful and follow precautions.
Were you able to get into a lot of the quarries in that area? That is one part of Michigan I have not collected in yet (from SE Michigan myself), but wouldn't mind getting up there. Are there a lot of collecting opportunities? 
Taylor V. Wrote:
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Also, the crystals seem
to have a dusting of another mineral covering
them, which to me seems like pyrite or
chalocpyrite.
Hi Taylor,
Possibly as you say or it may be Marcasite. You can check this with a loupe or a microscope.
Happy holidays,
Ron 
Thanks for the quick responses!
Ron, I found marcasite on other rocks in this quarry, so I'm guessing that it's marcasite that's dirtying my crystals. If it helps, the "dust" seems to have a goldish color to it, which is what had me thinking pyrite.
Scott, I did the acid test with vinegar, and the crystals I used fizzed pretty noticably. It's definitely calcite, as you said. This post was more of a reality check for me, I knew it was calcite, but I wanted it to be celestine so bad!
The Northeast of the Lower Peninsula is definitely worth a rock collecting visit, though. Maybe only a weekend trip, but theres definitely enough out there to make it worth your while. For the Alpena area, the only locality worth visiting is the Rockport Quarry. Its part of the Rockport Mineral Reserve, and seems to be public property (there were absolutely no No Trespassing Signs or fences) . The amount of material here is absolutely amazing. The entire quarry floor is covered in rock, and it has yet to filled with water. The size of the quarry is about 3/4 mile by 1/2 mile, so you could easily spend a day there. While there, we found calcite, dolomite, marcasite and a bunch of different fossils.
There are other quarries in the area, namely the Lafarge Company Quarry (still in operation), the Stoneport Quarry (operational), the Calcite Quarry in Rogers City (I wonder whats found there...operational), and the Paxton Quarry (not operational and filled with water, but marked with a host of No Trespassing Signs).
However, if your interested, theres more rock collecting to be found down near Tawas City. There's about 5 different gypsum quarries to the west of the city. We only visited two of them, the Alabaster Quarry and U.S. Gypsum Quarry, however both were operational, so we were forced to collect on the piles outside the actual property. We still came away with some beautiful orange alabaster, and a few pieces of selenite. There's also collecting to be found along the train tracks that leave the quarries. Still farther south, near Au Gres, is another quarry, but it's on an extension of the Bayport Limestone. We were unable to tell if it was private property because there weren't any No Trespassing signs, or gates on the road to enter it. We decided, against our better judgement, to take a quick peek. The quarry has obviously been long abandoned, and every building on it was old and dilapidated. Even on our 15 minute visit, we found some nice calcite, and geodes inside flint pockets. It's definitely worth a visit there if we can find if anyone owns the property and get their permission. There were a few other quarries in that area, but at that point it was raining pretty steadily, so we left and went home.
Overall, if your interested in Michigan collecting (as I am), its worth your time. Being from SE Michigan myself, I love to visit the UP and collect in the Copper and Iron Districts, but these areas are a little closer to home. If you have more questions, I'd love to answer them. I'll post picture of my other finds for your reference, Scott. All of my finds from Paxton Quarry came from a locality near there that I'm not willing to divulge to the general public (message me if you're interested).
Paxton Quarry
This photo is of the only unknown I have from this locality. Any ideas on this would be very helpful. It coated the outside of some shale outcrops, and is very fragile. The crystals seem to be dendritic.
The first of my dolomite specimens from Paxton.
My second dolomite specimen. The crystals are perfect rhombs and totally transparent. Paxton Quarry
Chalcedony after Dolomite. At least, I think the white coating is chalcedony.
First of my pyrite "suns".
Second Pyrite "Sun". Thanks for the info Taylor! I did not realize there was so much collecting available in that area, and will definitely have to give it a try when the weather lets up. That is quite a bit closer than some of the other trips I have taken, and should be easier to do when only a short amount of time is available.The UP is my absolute favorite place to go (not just for collecting), but it is quite a haul to get there. I have been trying to get an idea of sites a bit closer to home.
I have collected downriver, as well as up in the thumb, and in the northwest part of the lower peninsula (Traverse City area), but I have yet to collect in the southwest and northeast.
As for your first picture, I can't be sure, but it looks like gypsum growth, possibly "post-mining". It can exhibit some interesting crystal growth, and the fragile aspect fits with it. Paxton Quarry
Third Pyrite "Sun".
Rockport Quarry
Dolomite coating Limestone
Dolomite Vein, seems to be crystals of another type aswell. You're welcome Scott! I just have a few more photos here if you're interested, all from near Tawas City.
Au Gres Quarry
Calcite, not much more to say...
Never seen anything like this in Michigan before, and the exciting news is that they are everywhere at this quarry!
Alabaster Quarry
Beautiful Pink Gypsum var. Alabaster The closest collecting areas that I know of (and have visited) are the Wallace Stone Quarry in Bayport, and the Au Gres Quarry. I'm hoping to do a a better exploration of the Au Gres Quarry when the weather lets up ( 4 months from now :(). But I agree, nothing beats the UP! I haven't been up there since last spring, and I was dying to go back all summer, but its quite the drive to the amazing Keweenaw! I think most people assume that the Lower Peninsula is mineralogically boring, but there's defintely amazing collecting to be had here. 
Hi Guys,
Well I'm in the South Western side of MI, these places are about three hours to drive to, if either of you two want some company...I could meet you guys there :) I have a little quarry across from the Cheney quarry in Bellevue MI that I can get into, however, they were not deep enough as of last year to have anything really exciting, a few larger pyrite xls to about 1/2-1 inch but very very weathered, also a few calcites but not much else...
KOR
E Everett,
I think it would be great to collect together, especially since we missed meeting up at the Detroit show. Bellevue is not far from me at all, and would be an easy trip.
And, as far as anything exciting, that is okay. I just enjoy getting outdoors and collecting, especially when it is with other collectors and interesting discussion ensues. I am usually happy finding just about anything interesting. We should plan something when the weather lets up a bit. Scott,
Are you by chance going to Tucson this year? I'll be there, perhaps a meet there? If not we will for sure at least see how the Bellevue is coming along in the spring, the owner/op is a great guy who will take care of us :) It's been quite some time since I've been out hammering on something...I've bought a fix-r-up house and have spent the last year fixing it. Seems to put a dent in the rock collecting fund..but alas, I'm going to get some collecting in this upcoming year! so Plan on it :) Here is a link to one trip to this quarry. Trip Also a photo of one of the pyrite finds attached
KOR
E 
Just FYI; I'll be in Michigan this summer for about 3 1/2 weeks exploring some of the more geologic spots in the Northern Lower and all across the UP, eventually ending up in the Keweenaw for a few days. Not sure how much collecting I'll be doing, but if I see something that looks interesting...... B) Hey Capt,
Give me some dates, maybe we can work something out??
:)
E Everett,
Unfortunately, I don't think I will be going to Tucson this year. I had hoped to go, but I believe family circumstances and obligations will prevent my attendance. I understand about the house, too. Between working around my house, and working on my camper/RV, I have lost a bit of time and money the past couple years. Still, I would love to get together and collect, just to get out and get the experience of it. I wanted to go more last year but there were a few trips I had to cancel. I am hoping to get out quite a bit more next year, even if they are simple and inexpensive day trips. I am also hoping to get to the UP a bit more next year, even if I have to drive like mad to spend a couple days up there.
If you and Paul get some dates together and my schedule agrees, I sure wouldn't mind tagging along on that trip. Going through some of my old followed topics and came across this one, which I forgot all about.
Everett,
Have you had a chance to do much collecting this year? I haven't had the chance to do much at all, and I am hoping to remedy that a bit between now and the end of the fall. In another post I had recently, I asked about collecting in western Michigan, and Dana Slaughter mentioned an abandoned quarry in Bellevue, and I am wondering if it is the same one you referenced.
Just wondering if anyone got anything going along the lines of this topic/posting. Thanks-
