[176]
from this material in its genuine unadulterated state; the dealers in it, even amongst the mountains of Derbyshire, exhibit as much dexterity in adulterating and altering it as the most ingenious artizan in Duke's-place or the Minories could do. The article, when dug out, is of various colours, according as it is more or less tinged with mineral; and some of it of so deep a blue as to approach nearly to black. In order to render this saleable, the manufacturer exposes it to a gentle heat for a short time, and having thus warmed it through, places it in a much stronger for about half an hour, when it is drawn out, and exhibits those rich and resplendent purple tints which put to shame the lustre of the famous Tyrian dye. Great care, however, is requisite in this process.; for should the mass continue too long exposed to the fire, every colour would be discharged, and the whole reduced to an opaque white. Exclusive of this trick, the workmen have another mode of recommending their ware by artificial beauty. The masses frequently arc found imperfect, that is, indented with holes, where this happens to be case, a quantity of lead is melted and poured into the place, and afterwards being cut and polished with the spar, assumes the curious appearance of having been naturally combined with it.
