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One gem is thought to be a rare, 2nd Century head of the Greek hero Hercules made from obsidian, a type of volcanic glass.

Cryptotephra are signature volcanic glass shards that can range from 80-20 microns in size, which is smaller than the diameter of a human hair.

The sword, also on display in the exhibit, is a flat wooden club with a groove where razor-sharp obsidian - a type of volcanic glass - would have been wedged in.

In 2008, Brown University researchers revisited those lunar samples with new technology and found hydrogen inside tiny beads of volcanic glass.

The geochemical fingerprint of the cliff’s volcanic glass has been found all around the West, as well as in Canada.