169 
EARTHS, SILICEOUS. 55. Quartzum. 
c. Convergent. Born.ind. fofs. x.tab, 2./. 16. 
d. Decumbent. 
e. Seated in the manner of the prickles of an echinus upon a 
' larger cryttal or other foffil. 
f. Imbricate. 
Found in almoft every part of the globej particularly in alpine 
lituations, and is almoa exclufively confined to primitive 
' rocks, efpecially granite and mica flate : colour various fltades 
of white, brown, red, and yellow, fometimes mixed together: 
fraeraents indeterminately angular, with very iharp edges: 
does not lofe its tranfparency in the fire; caufes double re- 
fratlion : fpccific gravity from 2,650. to 2,888. contains 
filica93,o. alumina 6,0. lime t,o. Bergman. 
^““dogim. Coloured, pellucid, of a conchoidal texture, in a 6-fidcd 
tranfverfely ftriate prifm, 
Niirum fluor. Syst. nat. xii. 3. p. 85. n. 3. 
Cryftallus montana. Wall. fist, miner, l.p. 22O. n, 10, 
1. Blackifli. Baum, miner, 1. /, 232. ». 2. 
2. Clove-brown. Wall, fist, p, 222. n. 10, h. 
3. Red. Wall.fyfl. i. p. 22I, «• 'O- a. 
4. Fulvous. Wall, fist, I. p, 222. n. 10. e. 
5. Yellow. Wall.fiji. I./.222. b.io. d. 
6. Leek-green. Wall, ppft, i. p.z-t. n, 10. g* 
7. Grafs-green. Wall. fist. l. p, 222. n, lO. f. 
8. Sky-blue. Baum, miner. i,p. 236. 
9. Deep blue, Baum, miner. I. p. 23T, 
Found chiefly in veins abounding in rockcryftal, of varies de- 
grees of magnitude and tranfparency ; they are often fold tot 
gems, but may eafily be diftinguiflied by the different form 
of their cry Ifals and by their lelTer degree of hardnefs and 
lullre: they yield to the file, and like the rock cryftal, when 
two pieces are rubbed hard together, they emit a phofpho- 
refeent light in the dark, and exhale a peculiar empyreu- 
matic odour. 
Violet-blue, varying in texture, form and degrees of 
tranfparency. .. o- . j 
Nitnim violaceum- Syji. nat. xU. 3. p. o^. n. 3. • 
Cryftallus violacea. Wall.fiji. i. p. 2 Z 1 . n. 10. b. 
Amethyft. Kirovan mineral. \.p, 246. Schmeifier 
Anir.thylt, 
f/H/Kur j--- ^ - - 
■yameifon. l.p. 137* Bhomjon chem. 3./. 5 *®' 
VOL. Vll. — Y 
