Terra sigillata (or "sealed earth") is a name for two distinct items in antiquity. First, it is one term by which Samian ware was known. Secondly, it was a term for a medicinal soil from the island of Lemnos.
The latter was called "sealed" because cakes of it were pressed together and stamped with the head of Artemis. Later, it bore the seal of the Grand Signior. This soil's particular mineralic content was such that, in the Renaissance, it was seen as a proof against poisoning, as well as a general cure for any bodily impurities, and it was highly prized as a medicine and medicinal component.
Die fruhe Terra sigillata vom Monte Iato, Sizilien (Ausgrabungen 1971-1988) und fruhkaiserzeitliche Fundkomplexe aus dem Peristylhaus I.(Review) (book review)
Mar 01, 2000; BETTINA HEDINGER. Die fruhe Terra sigillata vom Monte Iato, Sizilien (Ausgrabungen 1971-1988) und fruhkaiserzeitliche...