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Identity HelpHelp please

14th Nov 2018 01:26 UTCLogan Miller

I’ve been scratching my head the past 3 hours trusting to decide what this mineral is.

It’s hardness is between 2-3

It reacts with HCl

If you have any idea what it is, or even a guess it would be much appreciated.

14th Nov 2018 01:58 UTCLogan Miller

-- moved topic --

14th Nov 2018 02:11 UTCPaul Brandes 🌟 Manager

Welcome to Mindat, Logan!

If your specimen reacts to acid, then you have a carbonate mineral. The question then becomes which carbonate is it? Based on the hardness you got, you probably have a piece of calcite.

14th Nov 2018 02:18 UTCKevin Conroy Manager

Where was it found?

14th Nov 2018 02:42 UTCReiner Mielke Expert

What reacts with the acid the green stuff or the white stuff it is on? What exactly did you test for hardness and how did you do it?

14th Nov 2018 03:32 UTCDoug Daniels

Agree with Paul, likely calcite. But as Reiner asked, which part was tested - the greenish part, the whitish part or (I'm adding this) the light-brownish part? And, as Kevin asked, do you know where it was found? Important info.

16th Nov 2018 17:34 UTCLogan Miller

Thanks for the help guys. Apparently the mineral were looking at is a very small red mineral that has been tarnished down to the greenish brown color you see on top.

Vanadinite

16th Nov 2018 18:34 UTCFrank K. Mazdab 🌟 Manager

That nub is what your class is using as a sample of vanadinite? And I thought our undergrad teaching collection was crappy... yikes!

16th Nov 2018 18:45 UTCReiner Mielke Expert

You are going to have to give us a better photo than that of the mineral in question.

16th Nov 2018 19:28 UTCThomas Lühr Expert

To me, it looks like epidote/clinozoisite in calcite, where the calcite is weatheted partly away. I can't see any red, sorry.

Test the hardness of the green stuff and provide a sharp closeup, if possible.

16th Nov 2018 19:59 UTCKevin Conroy Manager

I'm not sure how the "vanadinite" identification was made, but put that on hold. Where did the idea that the greenish brown crystals originated from a red mineral come from? I can see a yellowish mineral present. As Thomas suggested, sharp, focused photos and more data will help a lot.

Speaking of help, please see my comment in the "head scratcher" discussion.

16th Nov 2018 20:28 UTCPaul Brandes 🌟 Manager

Frank K. Mazdab Wrote:

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

> That nub is what your class is using as a sample

> of vanadinite? And I thought our undergrad

> teaching collection was crappy... yikes!

No kidding!! I wouldn't even think of giving my students such a miserable piece.

I for the life of me cannot see any vanadinite on that sample.

16th Nov 2018 21:37 UTCDoug Daniels

Certainly not vanadinite. Doesn't look like it, and it was stated it reacts with acid. The best that vanadinite would do there is dissolve in HCl, giving a green solution with a deposit of lead chloride, or in HNO₃ giving a yellow solution (according to Dana's System).

16th Nov 2018 22:32 UTCThomas Lühr Expert

Doug

Regarding the reaction with acid: he may have observed the reaction of the underlaying calcite matrix and not of the green stuff in question.

17th Nov 2018 01:40 UTCDoug Daniels

True; that's why an earlier poster asked what part exactly was tested.

17th Nov 2018 03:25 UTCGregg Little 🌟

Considering the mineral associations (assuming guesses from the photos is accurate) if we have epidote in calcite, or weathered out of the calcite, then a skarn environment is likely which might make the small greenish-brown crystals garnet. Might have to test the hardness again but you would need to isolate the mineral so as not to confuse the test with the carbonate mineral. A close-up of these brownish crystals would help to see is the form matches garnet.

17th Nov 2018 12:38 UTCEd Clopton 🌟 Expert

It's a long shot, but the arsenatian vanadinite var. endlichite from Shafter, Texas can present an appearance similar to the green mineral seen here.

17th Nov 2018 20:00 UTCFrank K. Mazdab 🌟 Manager

If the intention of that specimen is to indeed represent vanadinite for a mineralogy class, then perhaps a generous Moroccan mineral dealer might be willing to send all the broken vanadinite crystals that have undoubtedly accumulated on the bottom of crates shipped to Tucson or Denver to Logan's clearly under-funded geosciences department... ;-)

All kidding aside, this is actually a bit more serious issue. Broken or poor quality rock or mineral specimens don't effectively teach mineralogy, and they don't nurture in those students an aesthetic appreciation for minerals that keeps the hobby flourishing.

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