Old Eisenberg Original Mexico Silver brooch stone identification

[ivcmom75]

I’m getting mixed opinions on these stones. I think green onyx.  More thoughts please. Thank you, Sue

[bonjourami · Accepted solution]

Why dont you take this to the jewelry board?

[ivcmom75]

Ok, Thank you. 

[all_fakes]

One possibility is that these are opercula.  The operculum is a round piece used to seal the shell of a marine mollusc.

[maxine*j]

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@all_fakes wrote:

One possibility is that these are opercula.  The operculum is a round piece used to seal the shell of a marine mollusc.

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I think that's a very good guess.  Given the size of this piece, if the "stones" were actually "stones" (agate or onyx or chalcedony or the like), the thing would be awfully heavy, even for a coat pin.  I also read that the operculum's flat side, where it attaches to the animal, is rough and so opercula are usually in solid settings like the ones in OP's pin.