260 



Pyrites, not 

 magnetical« 



Metallic malle- 

 able iron* 



Whltifh gray, 

 crumbly earth. 



The cruft Is 

 probably black 

 oxide of iron. 



ON STONY AND METALLINE SUBSTANCES 



fo : fome of them, however, but very few, are of a larger 

 fize. The colour of thefe fmall globules is gray, fomclimcs 

 inclining very much to brown: and they are completely 

 opaque. They may, with great eafe, be broken in all directions : 

 their fracture is conchoid, and fhews a fine, fmooth, compact 

 grain, having a fmall degree of luftre, refembling in fome 

 meafure that of enamel. Their hardnefs is fuch, that, being 

 rubbed upon glafs, they act upon it in a flight degree; this 

 action is fufficient to take off its polifh, but not to cut it: they 

 give faint fparks, when ftruck with fleel. 



Another of thefe fubftances, is a martial pyrites, of an inde- 

 terminate form : its colour is a reddilh yellow, ilightly inclining 

 to the colour of nickel, or to that of artificial pyrites. The 

 texture of this fubftance is granulated, and not very ftrongly 

 connected : when powdered, it is of a black colour. This pyrites 

 is not attractable by the magnet ; and is irregularly diftributed 

 through the fubftance of the ftone. 



The third of thefe fubftances confifts in fmall particles of 

 iron, in a perfectly metallic ftate, fo that they may eafily be 

 flattened or extended, by means of a hammer. Thefe particles 

 give to the whole mafs of the ftone, the property of being 

 attractable by the magnet ; they are, however, in lefs propor- 

 tion than thofe of pyrites juft mentioned. When a piece of the 

 flone was powdered, and the particles of iron feparated from it, 

 as accurately as poffible, by means of a magnet, they appeared 

 to compofe about -^q of the whole weight of the ftone. 



The three fubftances juft defcribed, are united together 

 by means of a fourth, which is nearly of an earthy confiftence. 

 For this reafon, it is eafy to feparate, with the point of a knife, 

 or even with the nail, the little globular bodies above mention* 

 ed, or any other of the conftituent parts of the. ftone you may 

 wifh to obtain. Indeed the ftone itfelf may readily be broken, 

 merely by the action of the fingers. The colour of this fourth 

 fubftance, which ferves as a kind of cement to unite the 

 others, is a whitifh gray. 



The black cruft with which the furface of the ftone is coated, 

 although it is of no great thicknefs, emits bright fparks, when 

 ftruck with fleel : it may be broken by a ftroke with a hammer ; 

 and feems to pofTefs the fame properties as the very attractable 

 black oxide of iron. This cruft is, however, like the fubftance 

 of the ftone, here and there mixed with fmall particles of iron 



in 



