EARTHS. SILICEOUS. 46. Petrofilex. 153 



Flint, Kir-xvan l. /». 301. Schmeifjer I. /. 98. 

 Flint. Thomfon 'if. p.^\<^* So~joerby Brit min, f.SS, 

 Found in Britain^ France, Denmr.rky and other European coun- 

 tries, in detached pieces of various fliapes and fizes, and ge- 

 nerally covered uith a white calcareous coat: it is molt 

 common among chalk, an i often arranged in Tome kind of 

 flratarial order: .colour varying from honey - )'eilow to 

 brownifli-black, with variations often in the f me fpccimen 

 in the form of veins, ftripes, clouds or dots : it frequently 

 contains petrifaftions, particularly of the cruftaceous and 

 fmall coralline kind, and fometimes bears the impreiTion of 

 Echinitch and Be'.emnites : when two pieces are rubbed 

 fmartly together, ^hey phofphorefce and emit a pecU'iar 

 odc'Ur : when heated ii decrep-tate?, and becomes white and 

 opake : fpecihc gravity from 2,580. to 2,630. contains filica 

 yS,oo, lime 0,50. alumina 0,25. oxyde of iron 0,25. water 

 1 ,00. Klaproth. 



semipelluci- Light, nearly femitranfpafent. 

 <^^^' Silex Pyromachus. Sj/t. nat. xii. 3. />. 67. «. 2. 



Silex femipellucJduF. Jf'all.fyst. 1. pt 265. «, 6,' 

 Found in France^ Wir^mherg, Franconiay and Iceland^ generally 

 mixed wiih the laft, but more rare : colour white, honey- 

 colour, reddifh, blueifh, or variegated. 



\;itullinu:i Cryftallized \n a 3-rided dep re iTed pyramid, 



1, The pyramid fimple. 

 Werner Cron ft. mineral, /• 137* 

 Hoffmann Bergvis yourn, 1778. I. p, 282. 

 Found in Saxony y near Schneeburg^ 



2. The pyramid double. 

 Karfien Le she mineral. 1. p. II3, 

 Found m Saxon^y^ near Johanngeorgen^adt. 



46. FETROSILEX, Confiding of the greater part 

 fiiica, abont 22 per cent, of alumina, and 6 per 

 cent, of carbonate of lime: hardifh, lightifh, 

 found in primeval and ftratified mountains, with- 

 out luiire, breaking into indeterminate fragments, 

 • of a fpllntcry texture: melting before the blow- 

 pipe. 



apacu:* Nearlv opake, of a common form. 



Petrofilex, Lapi? corneus. Crond, miner. 92. 

 Hornftonc, Chert, Ktrt-.-anrnweral. l, p. ^o^, 



VOL. vir. — u 



