Chrysocolla[1] is a liquid which is found in the shafts already mentioned,[2] flowing through the veins of gold; a kind of slime which becomes indurated by the cold of winter till it has attained the hardness even of pumice. The most esteemed kind of it, it has been ascertained, is found in copper-mines, the next best being the produce of silver-mines: it is found also in lead-mines, but that found in combination with gold ore is much inferior.

In all these mines, too, an artificial chrysocolla is manu- factured; much inferior, however, to the native chrysocolla. The method of preparing it consists in introducing water gradually into a vein of metal, throughout the winter and until the month of June; after which, it is left to dry up during the months of June and July: so that, in fact, it is quite evident that chrysocolla is nothing else but the putrefaction of a metallic vein. Native chrysocolla, known as "uva," differs from the other in its hardness more particularly; and yet, hard as it is, it admits of being coloured with the plant known as "lutum."[3] Like flax and wool, it is of a nature which imbibes liquids. For the purpose of dyeing it, it is first bruised in a mortar, after which, it is passed through a fine sieve. This done, it is ground, and then passed through a still finer sieve; all that refuses to pass being replaced in the mortar, and subjected once more to the mill. The finest part of the powder is from time to time measured out into a crucible, where it is macerated in vinegar, so that all the hard particles may be dissolved; after which, it is pounded again, and then rinsed in shell-shaped vessels, and left to dry. This done, the chrysocolla is dyed by the agency of schist alum[4] and the plant above-mentioned; and thus is it painted itself before it serves to paint. It is of considerable importance, too, that it should be absorbent and readily take the dye: indeed, if it does not speedily take the colour, scytanum and turbistum[5] are added to the dye; such being the name of two drugs which compel it to absorb the colouring matter.