Back to IGS | FAQ | Contact

Natural Black Spinel?

Last December 2021, I imposed a question, that is, how can magnetite be distinguished from black spinel.
Since then, I found black pyramid shape stones, attached are pictures of what I have located.
I have scratched tested them with quartzite, topaz and synthetic ruby, of which synthetic ruby did leave an obvious mark.
These were found while walking around in the southwestern US
I don’t have a refractormeter to help distinguish whether or not they are black spinel. Nor do I personally know anyone who has a refractormeter.
Pictures attached of these stones, your insight would be appreciated.


Uploading: B8BC77A8-6F53-4168-8EFD-5A80FECCFE22.jpeg…
Uploading: 8BEEA511-DA04-43FA-AC27-E1877D22A5D1.jpeg…
Processing: B11C033F-617A-404F-828C-E6E7F5DC95D1.jpeg…
Uploading: F4F8D20F-24DC-4231-B036-1145249AD4DB.jpeg…
Uploading: 522165A6-9EEA-4AE0-AE62-CDCF8475917A.jpeg…

It could be magnetite. If a magnet is attracted to it, that’s probably what you found. .

Hi spinel has a hardness of 8 on mohs scale and magnetite is 51/2 to 6 1/2 so it is a lot softer
quartz hardness is 7 so should be able to make some form or mark if it was magnetite on a scratch test. Ruby hardness of 9 would make some mark on spinel?? the stone on the left certainly has the look of a spinel crystal and the top one I cannot see that well but it looks like a trigon on the crystal face, spinel crystals do have trigons on the crystal face , not sure if magnetite has trigons on the crystal face. thanks

1 Like

I forgot to mention if they are spinel they are usually found where sapphire deposits are. found, in my experience that is.

1 Like

I have been fortunate to have a gemologist examine the specimens and determine they are black spinel. Since then I have found quite a bite more, a few in the ten to twenty gram weight range. Some of the stones are impregnated with tiny reddish granular stones. Have yet find out what these reddish stones are.
Sapphires I have not found, yet, I will keep any eye open in my treks.
Thank you all for your interest

1 Like