154 EARTHS. SILICEOUS. 46. Petrofilex. 



Chert, Schmeifserminer. I. p, lOI. 

 Hornllone, Chert, ^hom/on chem, i- p.^i^. 



1. In texture refembline tefler fpl inters. 

 Petrofilex opacus. Wall.fyjl. min. i,p, 268. «. 9. 



a. With the colours alternating in ftrata. 



Silex polyzonias. Syit, nat. xii. 3. />. 71. », 16, 



2. In texture refembling larger fplinters. 

 Petrofilex opacus. Wall.fyst. min. I. p. 267. /». 8, 

 a. Of a greenilh colour. 



Silex virefcens. Syd. nat. xii. 3. p. 70. ». 12. 



Found in Sweden and Germanfy forming veins and beds ©f 

 mountains, and frequently in nodules like kernels in rocks: 

 colour ufually blue-grey, fometimcs grey, blue, and green 

 of various fhades : by breathing on it it difcovers an earthy 

 fmcll, and is fometimcs fo hard as to ftrike fire with fteel : 

 it decompofes fooner than flint, and does not take fo high a 

 poliih : in the fire it decrepitates and whitens : fpecific gra- 

 vity from 2,699. to 2,708. contains filica 72. alumina 22. 

 carbonate of lime 6. KirnKian, 



diaphanus, Semitranfparent, of a common form, 



Silex retrofilex. Syji. nat. xii. 3. ^ 70. n. 1 1. 

 Petrofilex femipellucidus. WalLfyli, \»p.z']\. «. 12. 

 Found with the laft fpecies; colour grey, white, ochraceous, 

 rofy, flefh-colour, brownilh-rcd, yellowilh or reddifh- 

 brown, green, or variegated : it often receives a fine polifh, 



crystallinust In rough cryftals which are frequently hollow within. 

 Beyer chem. annaU 1786. 1,/, 63. 2. /. 190. 



1. In 6-fided perfeft prifms. 



2. In 6-fided prifms, terminated each fide by convex furfaces. 



3. In 6-fided prifms, terminated each fide by a 3-fided pyramid. 



4. In cubes. 



5. In 6-fided tables. 



6. In double 4-fided pyramids.. 

 7« In double 3-fided pyramids. 



8. In double 3-fided deprefled pyramids, 



9. In fingle 3'fided minute pointed pyramid?. 



Found in Saxonyt near Schneehurg^ fometimes covered with a 

 thin earthy coating. 



