Well maybe not quite the Arkenstone, but I did feel like Bilbo Baggins for a second when I saw this in my sifter screen.
I'm guessing it is cut glass or crystal and I am guessing it was a necklace jewel ??
Also sifted the thimble. Found the rest with the detector. Found the bone-handled fork as I was digging for the lead tube thingy.
Honeysuckles are in bloom.
Jeff