About three miles south of Mullion, close to the shore, is the celebrated _Steatite_, or _Soap Rock_, which appears to run in veins[130] in the Serpentine, although Dr. Thomson is inclined to consider it as Serpentine itself in a state of decomposition. When it is first quarried it is soft, but by exposure to air it gradually hardens, although it never loses that peculiar _soapy_ feel which characterises it. Dillwyn & Co. of Swansea have, at present, the works in their possession, by paying to the proprietor, Lord Falmouth, a certain annual sum. Its value in the manufacture of China depends upon its infusibility, and the property it possesses of retaining its colour in the heat of the furnace; the first quality is to be explained by the total absence of lime in its composition, the latter by the very small proportion of metallic matter contained in it. There is, moreover, another purpose which it serves, depending upon the peculiar property of _Magnesian earth_ in preventing that degree of contraction[131] which always occurs in the fire when _Alumina_ and _Silica_ are alone made use of. Near this spot veins of _Native Copper_ may be frequently seen at low water during spring tides, and a mass of this metal was once raised which weighed 104 pounds. Copper is the only metallic substance that has been found in any quantity in the Serpentine formation; and this has never occurred except _native_, as in the above instance, or in the state of _Green Carbonate_, so that the mining adventurer need not anticipate much advantage from it.