Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/142

 130 fracture often conchoidal, breaking into large broad flakes with sharp edges; it is also frequently striped with red, which appears to be owing to the oxide of iron it contains ; small threads of tender yellow steatite are seen running through it, and it is often traversed by veins of whitish asbestos. The course of these veins is very straight, and by their intersections they form nearly regular rectangular pieces, thus disposing the rock to break in those directions. Sometimes this serpentine passes into a hard steatite, disposed in curved laminæ, and having at the same time a fibrous fracture.

The mica slate of the most southern part of the Lizard has a very brilliant lustre, is of a fawn colour, includes veins of quartz, and is evidently stratified. I was not able to discover any garnets in its composition.

By soap-rock is meant a kind of steatite, so tender that it may be cut as easily as new cheese. It is imbedded in the serpentine. Its colour is a pearly white or grey with red and blue veins, and when pure it has a sort of semi-transparence. On coming out of the quarry, it may be kneaded like a lump of dough, but after having been exposed to the air for some time, it becomes friable, owing, no doubt, to the evaporation of the great quantity of water it contains; it possesses the soapy feel in the highest degree, and pieces of hard stone are included in it, in pretty large quantity. It is used in the manufacture of porcelain for the same purpose as the kaolin, and on