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Identity HelpUnknown Ojuela mineral

10th Jan 2015 00:35 UTCAlex Earl 🌟 Expert

I was looking at some new minerals I got from my friend in Mexico, who self collected some specimens from Ojuela and sent a few to me. I got a piece of Microcrystals of Azurite and I came across this clear mineral that is hard for me to identify, any ideas? Any help would be appreciated, thanks!

10th Jan 2015 00:55 UTCsteven garza

Dear Earl;

Believe it or not, those might be small gypsum xls! They tend to be super gemmy colorless & clear, at that size & fairly common in mineralized gossans - especially where hydrated "-ates" are hanging.

Your friend, Steve

10th Jan 2015 03:40 UTCAlex Earl 🌟 Expert

Hello Steven,

At first I thought it might be Gypsum, but the crystal looks a little off for me to be Gypsum. The shape of the crystal is what is wierd for me, but I do think it being so clear is very interesting.

10th Jan 2015 06:17 UTCHomerbre

Alex,

That looks a lot like a nice water-clear calcite crystal. More than a guess, but not much more.

How is the collection coming?

Ron

10th Jan 2015 06:52 UTCAlex Earl 🌟 Expert

Hello Ron,

Yes, it could be Calcite.

The collection is coming along great, I still have the nice coppers, Azurite and Malachite you gave me, they look great in my display case! So far I have decided to focus on what I collect rather than collect a bunch of random stuff, although my display cabinet is full of nice pieces that don't necessary reflect my focuses. I have decided for the moment to focus on Tellurium minerals, and minerals from here in Utah, but that doesn't mean I will completely limit myself to them.

10th Jan 2015 11:13 UTCHomerbre

Alex,

I don't know that I have ever seen an actual tellurium mineral. Good luck with that!

Are you sure you don't want to focus on kryptonite-related minerals instead! :-)

Be good, my young friend.

Ron

10th Jan 2015 16:53 UTCAlex Earl 🌟 Expert

Ron,

I live in a good place to collect Tellurium minerals, although still very rare and hard to find, I do live near the Tintic district, with it only being about a 40-50 mile drive away. When I get my own car I plan on going down to Otto Mountain near Baker California, but that is about a 6 hour drive and 350 miles I think. I also have a friend in my local mineral club who is also interested in Tellurium minerals, and discovered many of the Otto mountain minerals and has one named after him, it's Thorneite.

I guess if I was feeling like (A)Lex Luther I would focus on Kryptonite :-D. Because my older brother is really into comics and superheroes, I actually bought him a potassium alum crystal that was rather large and green at Salt Lake Comicon from our local rock shop's booth who was selling them as Kryptonite haha!

10th Jan 2015 18:24 UTCDoug Daniels

If they had used a day-glo green dye it would have been even better for a kryptonite!

10th Jan 2015 18:30 UTCAlex Earl 🌟 Expert

Yes Doug haha! I wish they had!

I am still unsure, could the clear mineral be Gypsum or Calcite? The crystal structure seems wrong for both.

11th Jan 2015 13:13 UTCReiner Mielke Expert

A drop of acid will tell you right away. Gypsum will not fizz. Or if you poke it with a needle gypsum is much softer than calcite and will split in sheets that are slightly flexible, calcite will not.

11th Jan 2015 17:21 UTCAlex Earl 🌟 Expert

Reiner,

I figured I would try to see if it could be visually identified first, I will try a drop of vinegar, but I don't want to poke it with a needle, it is only about a .5mm crystal.

11th Jan 2015 17:49 UTCcascaillou

Under magnification, you could check for doubling (of facets edges, of contact matrix, or of inclusions...). That is non destructive test. Gypsum birefringence is only 0.010 so it could easily be ruled out if there's some obvious doubling.

11th Jan 2015 20:31 UTCUwe Kolitsch Manager

"... but I don't want to poke it with a needle, it is only about a .5mm crystal."

In such cases, I recommend an acupuncture needle (much thinner and sharper than any common needle).

12th Jan 2015 04:04 UTCcascaillou

Let's note that a needle being made of either steel or iron would likely scratch gypsum as well as calcite (as well as most of the other colorless minerals that have been reported from Ojuela). I keep thinking that doubling, if any, would be a more valuable info.

12th Jan 2015 05:10 UTCAlex Earl 🌟 Expert

Alright well I was able to get some time and I finally tested it. I used a dab of 5% vinegar on the end of a toothpick. After a few times of putting drops on it, there were what appear to be etchings left behind, the crystal still looks nice but it is certainly calcite.

Uwe, I have never thought of using an acupuncture needle for situations like these, thanks for the advice.

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