FMF - Friends of Minerals Forum, discussion and message board

[Shanester]

May 2022
Arkansas
Specific Gravity 3.88-3.94
6.9 grams
Sapphire?
Unusual?

[James Catmur]

Test the hardness (#8) and reaction to acid (#10). The SG looks to be a bit low for Corundum.

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

[Peter Megaw]

Looks somewhat like a diamond macle

[Bob Morgan]

Although the specific gravity is high for calcite, perhaps that's what it is. Try an acid test.

[James Catmur]

Not impossible for Arkansas. But SG is a bit too high

[Riccardo Modanesi]

Hi to everybody!
SG is a little low for corundum and a little too high for diamond, even if the appearance is typical for the latter one. Agree with who advices to try with an acid test, and I can add: try the hardness too, with iron, with glass and with anything else.
Greetings from Italy by Riccardo.

[Shanester]

Thank you all so very much for your time, and interest and mostly advice!

It is a privilege to be able to reach out to folks who have a passion, and bear knowledge without rights. That you share, is just plain awesome.

I don’t get to explore much as I like, and takes me an even longer to go through what I can pick up in just a minute. Always something new, ever time.

I’ll read through the tests 8 and 10 and do those. Let you all know soon as I get results. My SG was the lower one day I tested under a low front, and the other it was sunny and bright. Who wants to guess? I bet most of y’all would be correct.

My tools are ok for it I suppose. My gram scale reduces to .0 of a gram one digit in my favor to see .00. I tried my best to add nothing to the weight in water. I superglued a fishing line to it to suspend it. That’s life here on the river, just up out the bottoms on the right :)

Beautiful day! Be a blessing, seek peace and may you know that the Lord Jesus.. walks beside you.

[Firmo Espinar]

Hi everyone.

Another vote for some kind of corundum due to its pseudo hexagonal shape perimeter.

[Shanester]

Couple of scratch tests done. I tried it with a glass bead reamer (jeweler tool) which is diamond coated (claimed) and I can as expected scratch it with that, however it’s almost as if you can see where the test, but it didn’t really look to have done anything?? If that makes any sense. Also on unglazed white ceramic (mortise) it left no visible streak, so it clear to opaque to white.

Acid…is there any substitute for what to use, time adjustment? I have a cleaning product that is 10%hcl. If no then I will phone a friend :) Not near any hobby store for miles around.

I hope it is okay to post new pictures, since they are directly on subject. Wanted to share transparency.

Thanks again

PS it dug a rut through heavy mag glass lens

[James Catmur]

It looks like it is harder than glass but not as hard as diamond. That rules out Calcite so the acid test should do nothing.

With the crystal growth patterns, Corundum is a possibility. Where did you find it ('Arkansas' is a large area)?

Corundum is reported from Lake Catherine

https://www.mindat.org/loc-286741.html

James

[Shanester]

[James Catmur]

People 'salt' with non-local stones. That may well be what you have, so who knows where it is from. Hardness-wise and crystal form-wise it suggests Corundum but it could be a diamond given the location.

[Shanester]

[alfredo]

Don't waste your money on a thermal conductivity "diamond tester". They are designed for use on the flat polished facets of gemstones and give very unreliable results on rough stones and crystals.

[James Catmur]

Read this:

http://www.johnbetts-fineminerals.com/jhbnyc/diamondtest.htm

Visit a local jewellery store and ask them to test it, or talk to the Park staff is it is big for the diamonds found there

James