148 EARTHS. SILICEOUS. 42, Gemma. 



$, In 6-fided prifmr. 



a« The prifms perfett. 



b. The prifms terminated each fide by a 3-fidcd pyramid. 



Gmel.fyit. nat. 3. /. 446. /, x. f, 26, 



The faces fmooth. 



The faces diagonally ftriate. 



The margins of the prifmb truncate. 



Gmel fyst. nat. 3.^.447. t. i,f. 32. 



All the margins truncate. 



Gmel. fyst. nat, 3. p. 447. t.\, f. 28, 



Soiuuerby Brit, miner, tab, 43, 



9. In 1 2-fided prifm?. 



Gnurl, fyst^ nat. 3. />. 445. /. \,f. 25, 

 Am(rn, acad, l. p'\%z, t, l6.y*.25. 



Found in Britain and various parts of Europe y Madagnfcar^ 

 Ethiopia^ India, Syria, &c. fometimes in mafs, fcmetimes 

 cryilalized, in innumerable varieties of black, brown, pur- 

 ple, red, green, and yellow: texture foliated: fradure 

 commonly conchoidal : luftre glafTy and waxy : colour moll 

 commonly red: is brittle and eafily broken, and often ac- 

 traftcd by the magnet: fpecific gravity from 3,750, to 

 4,188. contains fihca 52,0. alumina 20,0. oxyde of iron 

 17,0. lime 7,7. Ffxvfuelin, 



QranadiU Hard, rather ponderous, red, of a parallelly fibrous tex- 

 hs* ture, melting with difficulty, in acicular prifmatic 



cryftals. 

 Rother Schoerl. Bindheim.chem. annal, 1792. z, p. 317. 

 Red Shorl. SchmeiJJ'er mineral, i. p. 81. 



Found in Sfwitxerland, the Pyrenees, Cadile, Hungary, and 

 Siberia, generally in Quartz or Granite: colour from that of 

 a peach-bloiTom to a blood-red : di^phanou?, fhining out- 

 v^rardly, breakirg into acute fragr^ienis, exhibiting convex 

 faces when broken tranfverfely, acquiring a high glody po- 

 lilh: the acicular cryllals fomecimes fcattered, fometimes 

 clavate, fometimes difpofed in a reticular manner ; fpecific 

 gravity 3,100. contains in 200 parts, filicii.114. alumina 

 ^9. magnefia i. oxydes of iron anci mangane/e 10, 



