Clams -- Velvety Jewels of the Sea: Aladdin's Cave on the Looney Front (TRAVEL)
Clam chowder. Clam bake. Clam up. Tight as a clam. As happy as a clam. OK, but you don't normally associate the filter-feeding, plankton-feasting bivalve mollusc -- you probably won't use that term either -- with gems.  Oysters, yes, but clams?