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Identity HelpUnknown clear matrix with pale yellow crystals

15th Aug 2015 15:53 UTCCameron Grieve

Hello any input on what this might be would be great. The matrix is clear and almost looks like fluorite. The yellow crystals are brittle like selenite. Again any thoughts would be great help. Thank you

15th Aug 2015 16:37 UTCScott Rider

Calcite (yellow) on fluorite (clear) is my guess... Can you provide focused images of the specimen? It appears the yellow is scalenohedral habit calcite on a cubic fluorite crystal(s). If we have a much better in focus image we can be more specific.

Also, we, well, other people here with far more knowledge than I will also request that you do some tests. How familiar are you with HCl? If not, you can also test how hard the two minerals by doing some scratch tests, this requires no acids and you may be more comfortable doing it that way. Calcite should scratch easily as will the fluorite. This link will give some insight on information of why we ask for hardness, it may give you some insight on the mineral world as well: http://www.mindat.org/article.php/1925/Mohs%27+hardness+testing+of+minerals+and+rocks

Also, try taking the image a little further away from the camera, it may focus better. Are you using a phone camera? The closest you can get on those is usually 5 or more centimeters so keep it away from the specimen so you can focus better.

:)-D

Scott

15th Aug 2015 16:41 UTCRob Woodside 🌟 Manager

Welcome to Mindat and thanks for trying Cameron. Both calcite and fluorite might show characteristic cleavage lines, if the photo was in focus.

15th Aug 2015 17:53 UTCEd Clopton 🌟 Expert

Can you give us an idea of where the specimen is from? That can help to narrow down possibilities.

15th Aug 2015 19:42 UTCCameron Grieve

I got it from a shop in castle Douglas scotland years ago unfortunatley i lost the tag stating its locality. I dont believe it is from the UK though.

15th Aug 2015 21:48 UTCColin Robinson

The shop would be Moorland Minerals and they sold/sell predominantly British material although they also have worldwide material for the more 'touristy' end of the market.

Not sure if they ever check out mindat so probably won't be able to give you answer. However, as others say, sharp photos and a few simple tests might help narrow things down.

15th Aug 2015 23:53 UTCGregg Little 🌟

I would also go with calcite on fluorite and sharper photos would definitely help. If you have access to a binocular microscope and don't mind a little invasive wet chemical analysis, apply a drop of 10% HCl to an inconspicuous spot at the base of one of the yellow crystals. If it is calcite you will get a quick burst of rapid effervescence. This would strengthen the probability of a fluorite association. If not fluorite then possibly dolomite but crystallographic properties should distinguish the two. Wet chemical test for dolomite is also HCl but the effervescence is much slower and prolonged as long as the acid doesn't reach the calcite.

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