^iotdada- 
V 
^fUAUus, 
EARTHS- SILICEOUS. 55. Qiiartsum. E67 
Fouftd in Various parts of England and Scotland, in Snxitxerlandi, 
Hungan, Sikjla, Bohemia, Saxony i more commonly pcl- 
kicid than opalce : colour moftly white, fometimes pale red, 
ycllowiJh or yellowifii-red i the cryftais generally in grains, 
fomctiaies resembling a Icidncy or a gem. 
Ot a conchoitlal texture, in a double ■bfided pyramid, n(«!: 
flriate. 
E With the pyramid perfsdl, 
Nitruin cryllallus. Syst. nut. xli. 3- h. 2, c. 
Senjoerhy Beit* min, I. iah, 4^5 4 ^' 
Gmel. fifi. not. 3. p- 44 )* f' 3 - 
i. With the margins of the common bale Crutreate. 
Gmel.fyft. not.. 3 . p- 44 j • 2. 
a,. Regulari 
Nitrnm cryflalltls. Sy/l, nat, xii. 3- P~ ^4. ®. 2, o 
fo. With all the faces unequal. 
Born^ied.fofs. I. p. z^.tab. 2-_/l 13- 
c. With the common bafe oblique, 
3. Pellucid. Bocc, muf. iah. 304* 
Fclluckl with opaJvC particles incladcd. 
'C^alte. 
Found near Bri/tol and Buxton, in Cornnuall, E>erbyjhire, aril 
Northumberland, and various parts of Europe: colour mollly 
white, fometimes reddifh orblacitifh; rarely hollow within ; 
the cryftals fometimes detached, fometimes clullered and ad- 
hering together in various forms, 
Whitej pellucid, of a conchoidal texture, in a 6-fiiieJ 
tranfverfely ftriate prifm. 
Nitrura lapidofum. ■Syrf. not. xii. 3. p. 84. n. s. 
CryHal'Ios montana. Wall. Jyst-.l- p- 2 ^ 7 - ”• 9 ' 
Scheuthx.ii.z\%. t.b. Wo^, Hafs. t. l. f. 1. 1,. b>. 
Gefn.fig. 18. f, U 2. Rumpb. muf. t. 52./. 5. 3. 4. 
Rock cryllal. Kirnxan 1 . p. .241. SchmeiJ/ir min. i . p. S9. 
Rock or mountain cryllal- Jamei/on min. i. p. 143. 
I . With the prifm obliquely truncate. 
jBflrv, ind.fofs. Z. p. 8g. tab. 1. /i 4, 
Jt. With the prifms terminating at one end in a 3-fided pyramid. 
Born, ind.fofs. Z- p. 89. Karft.Lefk.mn. t, p. 102. 
3. With the prifms terminating at one end in a 6-lided pyramli 
not ftriate. 
Wall, fyit. min. I. p. zij. n. g. a, 
a. The pyramid common to the two prifms. 
