FMF - Friends of Minerals Forum, discussion and message board

[rachael colborn]

Hi, I purchased this from a car boot sale back in 1997. I think it’s on a pink sandstone. At the time of purchase the lady said it was from a cave in the USA. That’s the only information I have but would love to know what it is.

[James Catmur]

Could you please do some tests? Maybe 7, 8 and 10 on this page

https://www.mineral-forum.com/message-board/viewtopic.php?p=19487#19487

[rachael colborn]

I tested it on porcelain and it left no colour. It does scratch glass. I don’t have any hydrochloric acid so put a piece that broke off in some bleach. It did not bubble but cleaned the broken piece nice.

[Michael Shaw]

Glad the bleach cleaned the specimen, but no bubbles with bleach is not a test that will help you identify the mineral. You can substitute household vinegar for hydrochloric acid. The vinegar made for cleaning is a little stronger and will produce bubbles if it is a carbonate like calcite.

[Matt_Zukowski]

Your piece looks like either quartz or a carbonate like calcite. If it is quartz, it will scratch glass and will not fizz in acid. If it is calcite it will not scratch glass and it will fizz in acid (hydrochloric acid is a strong acid and will make calcite fizz aggressively; vinegar (acetic acid) is a weak acid so you may need to test with a small bit of powder from the specimen).

[Pete Richards]

To my eye, your first pictures look like carbonate (probably calcite), but the last one looks like a rim of quartz around something else, maybe more carbonate. There are little reflective spots in your first pictures that look like they might be quartz peeking out from below a top carbonate layer,

So as you do your tests, consider the possibility that you may have more than one mineral.

[rachael colborn]

Hi James, Thank you for your help. I got hold of some strong vinegar. There were no bubbles on the outer chrysalis layer but there were some bubbles on the pink layer underneath. The attached picture is of the broken piece submerged in the vinegar.

[rachael colborn]

Don’t know if this helps but it is very, very sparkly in natural light. Looks lglittery when the sun shines on it.

[rachael colborn]

Cleaned it up and zoomed in.

[James Catmur]

Could you try to scratch the glass with the mineral that does not bubble and then the mineral that does.

It suggests two minerals:
scratch glass+not bubble=quartz;

not scratch glass+does bubble=calcite

[Jordi Fabre]

Is Quartz coated or mixed in certain areas with carbonates. While the carbonates fizz, the Quartz does not, and the Quartz parts scratches the glass, while the carbonate parts do not.

[rachael colborn]

Thanks again for your help. The crystal structure on the outside does not fizz and cuts glass so I’m assuming it’s quartz on the outer layer. Varying colours of white, pink and grey. The pink inside of the specimen also cuts glass but requires more force to do so. It does give off a couple of bubbles in vinegar but not a fizz. I think the inside bit could have some quartz mixed in with it.