*53 
EARTHS. SILICEOUS. 46. Petrofilex. 
Flint. Kir=wan I. joi. Schmeiffer I. 98. 
Flint. Thomfin 3. p- 319. Smuerby Brit, min, t. 83 . 
Found in Brilaiu, France,' Denmark, and other European coun- 
tries, in detached pieces of various lhapes and fizes, and ge- 
nerally covered with a white calcareous coat: it is moft 
common among chalt, and often arranged in fome kind of 
ftratarial order ; colour varying from honey - yellow to 
brown ifli black, with variations often in the fame fpecimen 
in the form of veins, ftripes, clouds or dots : it frequently 
contains petrifaflions, particularly of the crullaceous and 
fmall coralline kind, and fometimes bears the impreflion of 
Echinites and Bclemnites : when two pieces are rubbed 
fmartly together, .hey phofphorefce and emit a peculiar' 
odour : when heated it decrepitates, and becomes white and 
opake : fpecine gravity from 2,580. to 2,630. contains lilica 
98.00. lime 0,50. alumina 0,25. oxyde of iron 0,25. water 
1.00. Klaproth. 
nearly femitranfpareuf. 
Silex Pyromachus. Syji. nat. xii. 3. f. 67. «. z. 
Silex femipellucidus. Wall.fyst. i. p, 265. », 6. 
F ound in France, WirUmberg, Franconia, mdi. Iceland, generally 
mixed with the lall, but more rare: colour white, honey- 
colour, reddilh, blueifh, or variegated. 
Crylbllized in a 3-fided depreffed pyramid. 
1. The pyramid fimple. 
Werner Cronft. mineral, p. 137, 
Hoffmann Bergen, Journ. 1778. 1. p. 2 & 2 . 
Found in Saxony, near Schneeburg, 
2. The pyramid double. 
Karjien Lethe mineral. 1. p. 113. 
Found in Saxony, near ‘Johanngeorgendadt. 
46. PETROSILEX. Confifting of the greater part 
fitica, abpnt 22 per cent, of alumina, and 6 per 
cent, of carbonate of lime: hardifh, lightifh, 
found in primeval and ftratified mountains, with- 
out lullre, breaking into indeterminate fragments, 
of a fplintcry texture; melting before the blow- 
pipe. 
Nearly opake, of a common form. 
Petrofilex, Lapis corneus. Cronff. miner. 92. 
Hornflone, Chert, Kiravan mineral, l. 
VOL. VII. — U 
