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of opinion, 'tis not perfectly known, I shall here declare, as briefly as I can.
Having reduc'd the Ore into small stones, they calcine it first in a reverberating Oven, yet with a moderate fire, for fear of fusion, and driving away into the air part of the treasure, the volatile parts being by nature not perfectly mixt per minima with the fixt, as they afterwards come to be by industry and Art. And I have heard some of the more intelligent Mineralists say, that they judge their metallick labors and operations, to be many times not so much a reaping of silver ready made, as a kind of artificial compounding, and bettering of that, which nature had left dispers'd and imperfect. This Calcination serves chiefly to free the Mineral from many infirmities, that hinder the operation of the Quick-silver, and it serves also to discover, by the color of the fumes it yields, what corrosive mixture chiefly abounds in it, besides that it renders the one more tractable and plyant under the Mill-stone, which is to reduce it to a smal flower before the application of the Mercury. This is chiefly observed in those Silver-veins, that are of so hard and dry complexion, yet those which are usually more soft, abounding in oleaginous Sulphures, before burning are first ground into powder in such Mills as I have often seen in Glass-houses: and then they receive a gentle calcination, the Mineralist mingling therewith Ingredients sutable to the peccant humour, if l may so speak, of the Ore. As if, (e.g.) the mettal be sulphureous and antimonial, Rust and dross of Iron is found to be an excellent cure of this distemper: if Martial, and abounding in iron, then Sulphur and Antimony reduced to powder, is used as a convenient remedy for that disease. Sulphur hath a particular force, as I have found by experiment, to soften and dissolve Iron. But not only in this operation of Calcining, but also in applying the Quick-silver, there are so many different cases, in which different remedies are to be used, as there are Silver veins of several constitutions; of which elsewhere.
The Ore being ground, calcin'd, and curiously sifted, they divide it in several heaps, and then by lesser Essays, they find out how much silver is contained in every heap, where 'tis very ordinary to find only 6 ounces in 100. Pounds; sometimes 12; but if it yield 18. 'tis esteem'd a very rich vein: yet sometimes there are great Masses found all of pure silver, which is call'd Virgin-mettal.
Having discovered the quantity of silver contain'd in each heap, then proportionably they besprinkle them with quick-silver, and that not all at once, but at several times, stirring the Ore up and down. Then according to the diseases already discovered in the Vein by the fumes in the calcination, or according to any new symptoms, appearing in the operation of the quick-silver, convenient remedies are apply'd, if (e.g.) the Mercury give signes of being tocado (as they call it) i.e. if it appear
