Potstone

Potstone, Lapis Ollaris of the ancient Romans, a massive variety of talc-schist, composed of a finely-felted aggregate of talc, mica, and chlorite. It is generally of a grayish-green colour, sometimes dark green. It occurs massive, or in granular concretions. It is soft and easily cut when newly dug up, greasy to the touch, and infusible even before the blowpipe. It becomes hard after exposure to the air. It is made into pots and other household utensils, which communicate no bad taste to anything contained in them, and when greasy are cleaned by the fire. It was well known to the ancients; and Pliny describes the manner of making vessels of it. It was anciently procured in abundance in the isle of Siphnos (Siphanto), one of the Cyclades, and in Upper Egypt. Large quarries of it were wrought on the Lake of Como, from about the beginning of the Christian era to 25th August 1618, when they fell in, causing the destruction of the neighbouring town of Pleurs, in which it was wrought into culinary vessels, slabs for ovens, &c. It is quarried in the Valais, Moravia, Norway, Sweden, Greenland, near Hudson Bay, &c.