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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.

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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

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

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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

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