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Educationpseudocubic quartz

19th Aug 2018 22:23 UTCJennifer Cindrich

I am curious to find more information about pseudocubic quartz but have not had much luck but to find it listed here and on Amir's quartz pages.

-can anyone supply a link to more references/reading on it?

-How rare is it?

-At what other localities do they exist?

Thank you,

Jennifer

20th Aug 2018 00:18 UTCTom Klinepeter

I do not know what localities are on Amir's quartz pages but pseudocubic quartz crystals are found at the Tamminem Quarry, Greenwood, Oxford County, Maine, USA. They are not common..

20th Aug 2018 01:01 UTCKeith Compton 🌟 Manager

Jennifer

Try these:

http://www.minsocam.org/ammin/AM14/AM14_50.pdf

Frank C. Perham (1961) A Find of Rare Pseudo-Cubic Quartz Crystals in Maine, Rocks & Minerals, 36:5-6, 240-241

Flick, Heiner & Weissenbach, N. (1978). Pseudo-cubic quartz crystals of magmatic origin in rhyolites (quartz keratophyres) from the Rheinisches schiefergebirge. Mineralogy and Petrology - MINER PETROL. 25. 117-129.

20th Aug 2018 01:36 UTCPavel Kartashov Manager

Such quartz is known also in crystaline crusts within agates of Arts-Bogdo locality in Gobi, SE Mongolia.

20th Aug 2018 02:34 UTCJennifer Cindrich

Thank you so very much

20th Aug 2018 03:02 UTCAlfredo Petrov Manager

Quite prolific at one locality in New Mexico, whose name I don't remember. I have one from Madagascar too.

20th Aug 2018 04:03 UTCPaul Brandes 🌟 Manager

They are found on a bluff over looking the Pecos River east of Artesia in Eddy Co., New Mexico.

20th Aug 2018 12:54 UTCJennifer Cindrich

Paul, Have you ever heard of any coming from the Llano uplift here in Texas?

20th Aug 2018 13:05 UTCJennifer Cindrich

This is a good read for the New Mexico location.

https://geoinfo.nmt.edu/publications/periodicals/nmg/25/n3/nmg_v25_n3_p63.pdf

20th Aug 2018 14:52 UTCKelly Nash 🌟 Expert

That's a great article. I wonder how many of those localities can be accessed today. Here's a big pseudocubic quartz crystal from Arkansas, which is not generally known for these. I suspect any place that has a lot of quartz crystals is going to have an occasional pseudocube, while in other places (like Maine or New Mexico) they are a little larger fraction of the total, and it becomes a "locality" for them.

20th Aug 2018 15:58 UTCAlfred L. Ostrander

Can anyone explain to me why the varietal name pseudocubic quartz seems to be much more popular or accepted than a name truly relating to its crystallography such as rhombohedral quartz. If I am correct, the form is a predominant positive rhombohedron r {10_11}. The Miller indices are that of the positive unit rhombohedron of quartz. The negative z form may be present as very small faces and the m prism is usually absent but may also be present.

Is a "false" varietal form a better way of identifying this form than referring to it by the name of its true form? Is a varietal name to be preferred over a correct crystallographic form? Or is it just too hard to stop for a moment and learn the true crystallography over an implied false crystallographic form? The same can be said of the ever popular pseudo-octahedron. If it is a false octahedron, why not learn the true name of the form?

I realize crystallography is not all that easy. I have studied it for over forty years now. It can be confusing with all the different methods and approaches that have been used through out time. I have spent the last couple of months corresponding with a good friend as the two of us have very seriously explored the various approaches to crystallography. And we are not yet done. We have sometimes laughed and other times groaned at the confusion generated by different authors, each preferring their own method and nomenclature. How many know what a pentagon-tritetrahedron or a trigon-trioctahedron are? Yes, they are real forms. Still, real forms are being dealt with, not varietal names or pseudo names.

Sometimes I have to laugh as I remember an old Boy Scout song, "Catalina Magdalena Whoopinsteiner Wallendiner Hogan Mogan Logan was Her Name". And please, feel free to list any variants or spellings of this name you might have learned. Of course, please remember, she got it from her father just the same, same, same.

Call me crazy but I prefer dealing with real forms rather than pseudo forms.

20th Aug 2018 16:24 UTCAlfredo Petrov Manager

You're absolutely right, Alfred, but the problem is that (just like the Oxford English Dictionary) we are obliged to record names as they have actually been used in the literature, regardless of how illogical they are, because those are the terms users will search for. You (or Mindat) could start a campaign to change the common usage, and you may well be successful eventually, but it's a lot of effort overcoming linguistic inertia.

20th Aug 2018 16:28 UTCKelly Nash 🌟 Expert

Good grief. When I joined this site about ten years ago, I was immediately put off by someone who told me I should learn crystallography when I asked a question about dogtooth calcite crystals. Luckily, I ignored him, and have continued to enjoy and participate in Mindat over the years. As a matter of fact, I had several mineralogy courses on my way to a Geology M.S. forty years ago, and have studied crystallography (off and on) since then. Now that I'm a retired professional geologist, I have less and less patience with people who criticize others for using simple language rather than the "real" jargon that shows their superiority. Yes it's a rhombohedral form, but people call it a pseudocube because it looks like a cube. This includes many of the professionals who wrote the papers that have been shared here.

20th Aug 2018 16:36 UTCJohan Kjellman Expert

Alfred L. Ostrander Wrote:

-------------------------------------------------------

> Can anyone explain to me why the varietal name

> pseudocubic quartz seems to be much more popular

> or accepted than a name truly relating to its

> crystallography such as rhombohedral quartz.

I get what you mean Alfred but I suppose just because it is an oddity and an oddities often have "popular" names. Moreover, "pseudo-cubic" is not wrong or false because such crystals are actually nearly or almost cubic and "pseudo-cubic" has the advantage of shortly communicating the "odd" character to anyone hearing it, thus short for "hey, it is rhombohedral but almost looks like a cube".

cheers

20th Aug 2018 16:53 UTCErik Vercammen Expert

Well, all quartz is romboedric, but not all rombohedric quartz is pseudocubic.

20th Aug 2018 17:17 UTCJennifer Cindrich

Thank you for that lesson.

20th Aug 2018 17:29 UTCWayne Corwin

Nestor Tamminen gave me this pseudocubic quartz crystal, as a combo scepter also, from the Tamminen Quarry, Greenwood, Oxford County, Maine, USA. Collected by Nestor in 1971, given to me in 1981.

The cubic scepter quartz has a small milky quartz core you can see inside, the base is a larger broken milky quartz, with yellow/green cookite in many places.

20th Aug 2018 17:35 UTCJennifer Cindrich

Beautiful specimen!!

20th Aug 2018 18:42 UTCHolger Hartmaier 🌟

Pseudocubic quartz crystals are commonly found coating silicified limb casts of petrified wood here in Alberta, typically found along the Red Deer River valley around Drumheller. There are several references available on these occurrences, but I don't happen to have them handy at the moment.

20th Aug 2018 19:03 UTCAlfred L. Ostrander

Kelly, I wouldn't be been surprised if I was the one who questioned the use of dogtooth years ago. Participants on Mindat often make a big deal of other forms of nomenclature being superior based on science. Or, by whatever standard the IMA has set, as celestine, then celestite, then back to celestine. Varietal names of minerals are often contested, all without any suggestion of academic snobbery. But just question the proper use of crystallography or the difference between habit and crystal form and a suggestion of academic superiority comes into play? Would your professors in crystallography accepted dogtooth on a crystallography test because it is a common use of language? Or is it wrong to even ask the question without academic snobbery being tossed into play? I just don't buy it. Is it academic superiority if someone knows the difference between diorite and granodiorite? Good Grief! Or is that a term I should not be put off by? Not that I am but consider your usage when I think I made a legitimate request.

I accept the notion that common usage often gets deeply ingrained into language. Thank you Alfredo, John and Eric. Still, is it right to just keep on keeping on because that is the way it has been done for a long time? Consider this "Me and my friends went rockhounding." This form in the English language is common usage. But might it sound silly if I said "Me went rockhounding.". Or does the statement "I went rockhounding." make better sense?

And heaven help the poor soul who brings up anything metaphysical. Run for the hills. Bring up crystallography, run for the hills.

And Johann, it is almost a cube. But it is so much more. Why not indicate that? Short cuts often do come up short.

And Jennifer, I hope you learned something about pseudocubic quartz. It is more than a false form. It really is a rhombohedron as I described it. That does make it rhombohedral as a habit. You did ask for more information. I gave it as I see it. When pseudocubic quartz comes up in discussion, very few times does anybody bother to make note of what it really is. Thank you for your gracious reply. I did not intend to hijack your thread.

20th Aug 2018 21:28 UTCKelly Nash 🌟 Expert

Point taken, Alfred. I'm lucky this bulletin board isn't an exam. At least I didn't take you up on your offer to let me call you crazy. Keep fighting the good fight.

20th Aug 2018 22:07 UTCWayne Corwin

Here is a Square Herk I collected circa 2000.

It's from what was "Treasure Mt" in Little Falls, NY.

20th Aug 2018 23:39 UTCJennifer Cindrich

Very nice Wayne!

Here is one I found in a geode in central Texas. They are about 3mm in size.

21st Aug 2018 01:56 UTCWayne Corwin

Nice, look like big salt cubes !

21st Aug 2018 16:56 UTCEd Clopton 🌟 Expert

My micromount collection (which I sold about 10 years ago) included a few nice mm-size rhombohedral quartz crystals with pyrite that I collected from dump material at an old tin-tungsten-whatever mine (maybe the Juniper mine, though I was never sure) just north of Keystone, South Dakota in the 1990s.

21st Aug 2018 19:22 UTCScott Rider

Wayne, what an amazing specimen!!! I have 2 pseudo-cubic quartz from Eddy Co., New Mexico, and I've always wondered what they would look like without any of the included hematite coloring it... Now I know, seeing the example from Maine!!! Quartz may be a super common mineral, found in every single rock shop/show, all over the globe, but its still one of my favorite minerals!! These pseudo-cubes are so cool!!!

21st Aug 2018 21:57 UTCJeff Weissman Expert

Can I interest you in pseudo-octahedral quartz from Pargas, Finland?

22nd Aug 2018 01:39 UTCJennifer Cindrich

wow! (Jeff)

22nd Aug 2018 03:49 UTCDean Allum Expert

Jennifer,

The February 2018 issue of Rock & Gem contains an article about pseudo-cubic quartz crystals contained in Keokuk geodes.

-Dean

22nd Aug 2018 18:10 UTCJennifer Cindrich

Dean,

That is an interesting article. I have found several with the chalcedony coating as well. The pseudocubic quartz in the geodes I find are contained in about every 1 in 10. Which doesn't seem very rare to me.

Jordan Marche II states,

'then these types of Keokuk geodes might represent the most common occurrence of pseudocubic quartz crystals that are currently known.

At present, I know of only two localities where geodes of this type have been found. Both are located in the Hamilton, Illinois, area.'

https://tghost.me/download_file/RX6fd70XZv3AbKf/2018-02-01%20Rock&Gem_%28GeoHamrah.ir%29.pdf

Add my locale

2nd Sep 2018 18:08 UTCDon Windeler

I've been meaning to add to this thread, and finally got around to digging up the specimens and taking a couple pics.

Earlier this year I bought a pseudocubic amethyst thumbnail from Madagascar at an online auction. Just a few weeks later I ran across another from Zimbabwe that was so similar in presentation that I had to pick it up to make a pair. Pictures from similar angles are below.

Specimen on the left is attributed to the Kahore Mine, Karoi, Zimbabwe. (This mine is not listed in MinDat.) About 2.7 cm tall, with the longest edge on the crystal 1.7 cm. Specimen on the right is from Ambohimasina, Antananarivo Province, Madagascar. 2.2 cm tall, longest edge 1.1 cm.

Front views:

Looking down the ends:

Backsides:

Cheers,

D.

7th Sep 2018 17:10 UTCDonald B Peck Expert

Don

Neat specimens!! But they look more "pseudotetragonal" than pseudocubic! ;<}

Don

7th Sep 2018 17:43 UTCBob Harman

For the first time I looked at this thread and the R & G article. If those pix are what JENNIFER and DEAN and the article are referring to as pseudo cubic quartz crystals, they are also very common here in Indiana geodes. In fact so common and of such middling quality that I had really never given them much of a second look! I do have several....of a bit better quality, but have never photographed them. CHEERS.......BOB

7th Sep 2018 18:21 UTCBob Harman

Here are 2 of mine from Monroe County Indiana. they were kept, not because of the quartz, but because both had micro malachites about

1 mm - 3mm. One is on aragonite, coating the pseudocubic quartz. The other seems to be on small hemispheric calcites. Malachite is very rare in Indiana geodes. For this thread tho, concentrate on the quartz, in both photos best seen in the left portion of the geode cavity.

If these postings on the pseudocubic quartz in geodes had been on the Midwest geode thread, it might have caught my attention earlier. CHEERS.....BOB

7th Sep 2018 20:20 UTCMatt Neuzil Expert

The form of quartz you inquire about also occurs in Ohio.

https://www.mindat.org/gallery.php?loc=54977&min=3337

9th Sep 2018 17:16 UTCDon Windeler

Donald B Peck Wrote:

-------------------------------------------------------

> Don

>

> Neat specimens!! But they look more

> "pseudotetragonal" than pseudocubic! ;<}

>

> Don

Very true -- I've wondered about the "pseudocubic" term before and agree it's a bit sloppy for the pieces I showed! Just because it looks 90-degree-ish doesn't make it a cube.

Is there any theory as to what causes the quartz to grow in these odd forms? There are examples in this thread from both igneous and sedimentary environments.

Cheers,

D.

9th Sep 2018 17:29 UTCErik Vercammen Expert

The termination of a quartz crystal is mostly formede by two rombohedrons, and together they may look like a 6-sided piramid. But if only one of the rombohedrons is present (or is much larger than the other), the termination looks like cubic (pseudo-cubic) because the angle of the rombohedron is very near to 90 ° (87 ° if I remember it well). And if the prism is absent or only poorly developed, the crystal as a whole gives the impression of being a cube, whence the description 'pseudo-cubic'

10th Sep 2018 14:03 UTCEd Clopton 🌟 Expert

I have also seen quartz crystals with only one terminal rhombohedron developed in Warsaw Formation geodes from the Keokuk, Iowa area (most of which actually come from neighboring Missouri and Illinois). Must be something about the low-temperature sedimentary geode environment that favors that crystal habit.

3rd Oct 2018 20:48 UTCRonald J. Pellar Expert

Here is my favorite!

26th Mar 2023 14:21 UTCJulee Monahan

Here is one I found in 2019 (Coos County, NH) prospecting near some of Peter Samuelson's, Carlton Holt's and Cliff Trebilcock's old localities. Peter, Carlton, Cliff, Frank Perham and Al Falster have all seen and positively ID'd this for me, and all but Cliff were able to hold this in their hands with sparkling eyes and child-like grins! Al handwrote and signed the label for me to make it "official", but only after explaining pseudocubic was Maine/New England Rockhound "slang" and so he used the "proper" term for the label instead as a "Single Dominant Rhombohedral Quartz xl" which of course, Frank had a laugh and an eye-roll over! I also have another of these I found a couple years later, about 1/4 of the size.

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