I purchased these earrings recently. No provenance at all, the shell looks authentic at least 
and for what it’s worth, the veining on the turquoise beads does go through to the inside, as does the colour. The little red beads at top seem to be plastic, the findings are sterling.
The beads are strung on cotton (?) string that is quite grubby in places.
My main question is about a residue that’s found between many of the beads. It’s a chalky white powder, often with some gummy darker stuff underneath. It comes off easily with a fingernail or toothbrush; underneath it, the beads look just fine. I’m not sure if it’s residue from being worn, a substance from the string (the string itself looks a bit powdery in places – or perhaps it was waxed?), or something else.
Photos below… excuse unappetizing sight of chapped fingers! All comments welcome, as always.
