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Identity HelpGuess-the-mineral quiz!

27th Aug 2018 17:39 UTCUwe Kolitsch Manager

Which mineral is this twinned crystal? (Hint: it's grown on grossular.)

[EDIT: Later added to the locality page: https://www.mindat.org/photo-906570.html ]

27th Aug 2018 18:03 UTCKevin Conroy Manager

diopside?

27th Aug 2018 18:06 UTCUwe Kolitsch Manager

Nope.

27th Aug 2018 18:14 UTCRichard Gibson 🌟

sphalerite?

27th Aug 2018 18:25 UTCUwe Kolitsch Manager

Nope.

27th Aug 2018 18:29 UTCNick Gilly

Bixbyite?

27th Aug 2018 18:42 UTCKyle Bayliff

I would guess clinochlore.

27th Aug 2018 18:57 UTCHorst Schabereiter

Magnetite is one of my ideas. Horst Schabereiter

27th Aug 2018 19:23 UTCDavid Baldwin

Secondary grossular?

27th Aug 2018 19:38 UTCJeff Weissman Expert

Vesuvianite

27th Aug 2018 19:48 UTCJake Harper Expert

Great idea, Uwe,

Reminds me of a wonderful, game mindat used to provide - the mineral quiz!

It was great fun, highly educational and I’d like to petition here to bring it back again!

BRING BACK THE MINERAL QUIZ!

My guess: Clinochlore

27th Aug 2018 20:10 UTCWayne Corwin

Pyrite

27th Aug 2018 21:19 UTCKnut Eldjarn 🌟 Manager

Rutil?

27th Aug 2018 21:29 UTCAlex Homenuke Expert

Pyroxene

27th Aug 2018 21:58 UTCJohn R. Montgomery 🌟 Expert

Vesuvianite

27th Aug 2018 22:08 UTCMichael Hatskel

Perovskite

27th Aug 2018 22:12 UTCRuss Rizzo Expert

John Montgomery Wrote:

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

> Vesuvianite

That's what I was thinking too, but the angles of the crystal faces didn't seem right to me. Of course crystallography is not my strong suit.

27th Aug 2018 23:00 UTCNiels Brouwer

Spinel?

27th Aug 2018 23:37 UTCRichard Gunter Expert

Ilvaite? It would be a great help to know where it is from. That is often half the battle in mineral id.

28th Aug 2018 00:51 UTCKeith Compton 🌟 Manager

I would have said that the brown xl was Grossular

28th Aug 2018 02:03 UTCKevin Conroy Manager

Guess #2 - augite?

28th Aug 2018 02:09 UTCMartin Rich Expert

Seems to me like epidote, view more or less along [010].

I'm not sure if this is a twin.

28th Aug 2018 02:38 UTCSteven Kuitems Expert

Pyrochlore?

28th Aug 2018 05:59 UTCAlex Homenuke Expert

Second guess - smokey quartz

28th Aug 2018 07:48 UTCDon Windeler

Definitely would be nice to have the locality, even if only regional -- would help with possible geologic associations.

I'll throw a good old skarn association into the ring: epidote.

Cheers,

D.

28th Aug 2018 08:45 UTCUwe Kolitsch Manager

Martin Rich and Don Windeler are the winners - it's epidote (SXRD-analysed)!

It's from here:

https://www.mindat.org/loc-123337.html

Here is a pseudo-octahedral crystal from the same find (similar, but much bigger xls are known from Pakistan - https://www.mindat.org/loc-156277.html):

https://www.mindat.org/photo-906569.html

28th Aug 2018 13:40 UTCKevin Conroy Manager

Uwe, thank you for posting this, it was fun!

28th Aug 2018 14:48 UTCLarry Maltby Expert

Uwe, I agree with Kevin,

This was an interesting thread to follow. I had no idea what the crystal was and could not even guess. The other benefit of this idea was that you called our attention to the locality. When I went to the gallery of minerals from there, I found the micro copper and cuprite to be especially neat.

Larry,

28th Aug 2018 17:36 UTCMartin Rich Expert

Yeah! I have won a milion ton of coal. :)

I think it's not a twin. I have made a similar drawing of epidote. The view is parallel to b-axis. Twin plane of epidote is in the most cases (001).

28th Aug 2018 18:14 UTCUwe Kolitsch Manager

Have you tried to draw a twin?

I wonder if the Goldschmidt atlas shows some similar twins (never checked).

1st Sep 2018 01:26 UTCMartin Rich Expert

I have investigated this image a lot and the result is a smoking brain!

First, I thought it is a single crystal. The two triangular faces have a convex angle and I tried to make a crystal drawing, but the result was not satisfying for me. After a while, I noticed there is a concave angle between the triangular faces. See follow image (sorry for the occupation of your/Harry's photograph):

Goldschmidt do not show such twins. There are some drawings of twins, but all are elongated after a-axis (old crystallographic orientaion).

1st Sep 2018 02:12 UTCMartin Rich Expert

I used Goldschmidt's Fig. 16 of epidote as base for my drawings (the large and ugly epidote crystals from Pakistan are showing this shape).

I modified this shape with the result of a bipyramidal crystal shape (with small faces of the -101 pinacoide). For better presentation not in right crystallographic setting shown.

In most cases epidote twins have the twin plane (001). So I used this plane for my twin of bipyramidal crystals and the result is similar of a spinel twin.

Voilà!

Crystallographic setting also twisted.

PS: Drawings made with Kristall2000. Maybe I'm wrong and some other mindaters have better ideas.

1st Sep 2018 16:35 UTCDonald B Peck Expert

I think they look pretty good, Uwe.

10th Sep 2018 19:58 UTCMartin Rich Expert

Uwe, should I add the last drawing as a child photo to https://www.mindat.org/photo-906570.html ?

11th Sep 2018 07:27 UTCUwe Kolitsch Manager

Yes, good idea! In the caption refer also to this thread (I have now done so with the colour photo.)

11th Sep 2018 10:49 UTCHarald Schillhammer Expert

Where is the "like" button?

12th Sep 2018 22:37 UTCMartin Rich Expert

Done.

I added the drawing under the minID of the photo as miscellaneous, so it is user gallery only (not very helpfull).

Harry, the "like" button is there where you will me never find and this company earn millions of $ with this button. Mindat do not have such button, so mindat is poor like a church mouse! :)

13th Sep 2018 08:42 UTCUwe Kolitsch Manager

It's site-wide but the child photo icon is not shown.

If you click on the colour photo, however, the arrow to the child photo is shown.

It's also listed on the locality page under photos/miscell. photos.

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