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Some have suspected that the piedras del Inga or Incci,described by the same author as being untranlparent andof a leaden colour, and which were made into mirrours bythe ancient Indians, consist of platina mixed with a stonymatter.. This mineral cannot be the same with that towhich he gives the name of platina in the foregoing para-graph, for he expressly mentions that the piedra del Ingois soft, and liable to be broken by a slight blow. The Incastone is now pretty common, and as the French translatorof the papers on platina (fee page 447) observes, appearsto be no other than a ferrugineous mineral of the pyritesor rather mundick kind.

Alonso Barba mentions a substance, under the name ofchumpi, which seems to have more resemblance to the pla-tina of d’Ulloa. He describes the chumpi as a hard stone,of the emery kind, participating of iron, of a grey colourshining a little, very hard to work because it resists the firemuch, found in Potosi, Chocaya, and other places, alongwith blackish and reddish ores that yield gold. If platinais really found in large masses, either generally or only nowand then, one. might reasonably expect those masses to besuch as are here described.

Of the same kind perhaps also is the mineral mentionedby several authors under the name. of Spanish emery, Smin'sHijpanica, which should seem, from the accounts given ofit, to be no other than platina or its matrix. The Jmirisis said to be found in the gold mines, and its exportationprohibited; to contain films or veins of native gold; to bein great request among the alchemists; to have been some-times used for the adulteration of gold; to stand, equallywith the noble metal, cupellation, quartation, antimony,and the regal cement; and to be separable from it byamalgamation with mercury, which throws out the smirisand retains the gold; properties strongly characteristic.; of

piatina,.