Unmelting ice, a blob of quicksilver, a conch shell with the sound of the sea, an aquamarine of epical proportions, a captured ripple, a weeping stone.
The term gems is used for conveniance sake. Could have called it quintessence or something, but gems is pretty straighforward.
I doubt their proportions are that epic, considering you can carry around thirty of them without encumbering you (and presumably in a nifty little pouch)
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