in Natural History, a rich iron ore found in large masses of no determinate shape or size, extremely hard, and very heavy. It is usually of a dusty brownish red on the surface; but when broken, is of a fine bright iron-gray, but not without some tinge of redness; and is tangled all over with thinning streaks, which are small flakes of a foliaceous tale, highly impregnated with iron. It is also sometimes very red, and then usually contains veins of gold. It makes no effervescence with any of the acid menstruums; and is found in some of the Greek islands, in Tuscany, and some parts of Germany.
Dr Lewis is of opinion, that some kinds of emery may contain the metal called platina, and on this subject has the following curious observations. "Alonso Barba mentions a substance called clumpi; which is a hard stone of the emery kind, participating of iron, of a gray colour shining a little, very hard to work, because it resists the fire much, found in Potosi, Chocaya, and other places, along with blackish and reddish ores that yield gold. If platina is really found in large masses, either generally or only now and then, one might reasonably expect those masses to be such as are here described.
"Of the same kind perhaps also is the mineral mentioned by several authors under the name of Spanish emery, smiris Hispanicus, which should seem, from the accounts given of it, to be no other than platina or its matrix. The smiris is said to be found in the gold mines, and its exportation prohibited; to contain films or veins of native gold; to be in great request among the alchemists; to have been sometimes used for the adulteration of gold; to stand, equally with the noble metal, cupellation, quartation, antimony, and the regal cement; and to be separable from it by amalgamation with mercury, which throws out the smiris and retains the gold; properties strongly characteristic of platina, and which do not belong to any known substance besides. This debasement of gold per extracitum smiridis Hispanici is mentioned by Becher in his Minera arenaaria, and several times hinted at in his Physica subterranea. Both Becher and Stahl indeed call the substance which the gold receives from the emery an earth, whereas platina is undoubtedly a metal; but this does not at all invalidate our supposition, for they give the name of earth also to the substance which copper receives from calamine in being made into bras, which is now known to be metallic.
"From these observations I have been led to suspect, that the European emeries likewise might possibly participate of platina. If this was certain, it would account satisfactorily for the use which some of the alchemists are said to have made of emeries and other ferruginous ores; and we should no longer doubt, or wonder, that by treating gold with these kinds of minerals, they obtained a permanent augmentation; that this augmentation, though it refitted lead, antimony, aquafortis, and the regal cement, was separable, as Becher owns it was, by quicksilver; and that, when it exceeded certain limits, it rendered the gold pale and brittle.
"If emery contains platina, I imagined it might be discoverable by boiling the powdered mineral in melted lead, and afterwards working off the lead upon a telf or cupel. The experiment was made with eight ounces of the finest powder of common emery, and the same quantity of lead; which were covered with black flux to prevent the scorching of the lead, and urged with a strong fire for two or three hours. The lead became hard, rigid, of a dark colour, and a granulated texture, as if it had really imbibed some platinum from the emery; but in cupellation it worked almost entirely off, leaving only a head about the size of a small pin's head, which was probably no other than silver contained in the lead.
"I repeated the experiment with some variation, thinking to obtain a more perfect resolution of the emery by vitrifying it with the lead. Two ounces of fine emery and six ounces of minium were well mixed together, and urged with a strong fire, in a close crucible, for an hour: they melted into an uniform dark brownish glass. The glass was powdered, mixed with four ounces of fixed alkaline salt and some powdered charcoal, and put into a fresh crucible, with some common salt on the surface: The fire was pretty strongly excited; but the fusion was not so perfect as could be wished, and only about two ounces of lead were found revived. This lead had suffered nearly the same change as that in the foregoing experiment; and like it, gave no appearance of platinum on being cupelled.
"It seems to follow from these experiments, that the emery employed in them contained no platinum; but as it is not to be supposed that all emeries are of one composition, other sorts may deserve to be submitted to the same trials. As gold is contained in some parcels of common minerals, and by no means in all the individuals of any one species; platinum may possibly in like manner be found in some European ores, though there is not the least footprint of it in other parcels of the same kind of ore."