Medicina hydrostatica, or, Hydrostaticks applyed to the materia medica shewing how by the weight that divers bodies, us'd in physick, have in water : one may discover whether they be genuine or adulterate : to which is subjoyn'd a previous hydrostatical way of estimating ores / by the Honourable Robert Boyle ...

SECT. V.

BUt there is one Kind of Mine∣rals, that I have observed to impose on Men so often, that I think it necessary to take a particular no∣tice of them in this place. For, not to mention Examples, that I might draw out of the Books of Travel∣lers and Navigators, I have met with I know not how many, that have built great hopes, and some, (which is worse) that have been at Char∣ges upon those illusory Expectati∣ons of great matters from Marcasites. And, I remember, I have had sent me, or brought me, not only from Places nearer home, but from hotter and col∣der Countries of the Indies themselves, Fossiles, whereof I was earnestly de∣sired to give my Opinion, that I found to be but Marcasites: And ma∣ny of these Fossiles having two Qua∣lities, that make them very fit to

delude the vulgar, and the unskilful, namely, first, a Multitude of shining streaks, or other glistering parts usu∣ally of a Colour near enough to That of Gold, and sometimes to That of Sil∣ver; and then, a Ponderousness usu∣ally not inferior, at least, to that of true Metalline Ores; Marcasites, I say, being thus fitted to delude the unskilful, I have had much ado to un∣deceive some, that brought or sent me them from America, of the plea∣sing Confidence they had entertain∣ed, that these promising Fossiles were Lumps of rich Ore of Gold, or Silver. Wherefore since their Pon∣derousness (which is the Criterion of Minerals, I am now treating of,) is One of the Two chief Things that delude so many, I think it expedi∣ent, to subjoyn some few, but vari∣ous, Instances of the Specifick Gravity of Marcasites, whereby it may appear, that some of them are, Bulk for Bulk, far more ponderous than divers true Metalline Ores, that I have try'd, have been found to be. And indeed

this great Ponderosity has several times invited me, before I made any Artificial Tryal of propounded Fos∣siles, and sometimes before I took them out of the Bags or Papers to look on them, to judge, tho' perhaps to the Surprize of those that brought them, that they were not true Ores, but Marcasites. And, because this Mistake is speciously grounded, and has deceived many, whereof some have undertaken Voyages betwixt Europe and the Indies, upon confi∣dence of the value of these glistering Stones; I shall decline a little the Me∣thod of this Paper, which confines me to the Hydrostatical Way of ex∣ploring Minerals, to advertise those whom it may concern, that they may easily try almost any Stone, that, by its great Weight and Lustre, they suspect to be a Marcasite, if they put it, either within a Crucible, or, without One, into a well-kindled Fire, and blow now and then upon it with a pair of Bellows. For, by this means, the Sulphur, wherewith

Marcasites are wont to abound, (so that I remember, that even by Destil∣lation in a close Vessel, I had ℥iv of good Brimstone, like the vulgar, out of lbiij of the Stones) will take Fire, and burn with a Flame for the most part blew, like that of com∣mon Sulphur. And, if when it cea∣ses to flame and smoak, you take it out of the Fire and let it cool, you will find it deprived of all the gau∣dy appearance of rich Metal it had before, and turned to a brittle blac∣kish Substance, differing enough from That of a Metalline Ore, more strictly so called. These last words I add, be∣cause, in a lax Sense, 'tis easie to shew, that Marcasites, at least those that I have tryed, may be looked upon as a kind of Metalline Bodies. For, be∣sides that I have found divers of them to contain Particles of Copper, I found all, that I purposely exami∣ned, to contain, and some of them plentifully enough, Corpuscles of Iron or Steel, as plainly appeared, when, after the newly mentioned

Calcination, (for with crude Mar∣casites I found not the following Tryal to succeed) I applyed to the pulverized Remains a vigorous Load-stone; to which great multi∣tudes of Martial Corpuscles quickly adher'd. And, I remember, I found in a Catalogue of the Fossiles of Mis∣nia, published by the experienced Kentmannus, that, under the Head or Title of Pyrites, he brings in seve∣ral Marcasites, whereof some con∣tained Copper, others Silver, others Gold, and others both the last nam∣ed Metals; which brings into my mind, that, having presented, among other English Minerals, a curiously shaped, and very fine Marcasite, to a Virtuoso, that is now Overseer of one of the Emperors best Mines; He quickly examined it by a peculiar Way, not known to me, hoping to find in it some Gold or Silver; but, instead of that, obtain'd a Portion of running Mercury, which he was pleased to present me, and which, I presume, I may have yet by me.

Tho' I thought it needful to give the foregoing Caution about Mar∣casites, for the Reasons before ex∣prest, yet my Design is, only to keep the less skilful from being deluded by their promising appearance. For otherwise I do not deny, but that 'tis possible for a skilful Artist, to make (at least of some sorts) of them a gainful use; either by fixing the Volatile Gold or Silver, that may be found in some of them; or, by graduating Silver, by their means; or, perhaps by some other Ways, that I can but guess at. But (to add That on this occasion,) that, for which I much more value Marcasites, is, That (NB) somewhat more than bare Conjectures make me think, that, being dexterously handled, and perhaps even without Additions, they may afford very noble, as well as uncommon, Medicines; and par∣ticularly in Continual Feavers, tho' their Operation be usually scarce sen∣sible, but by their good Effects.