72 
A SYSTEM OF 
SECT. LXVL 
H. Rhombic Quartz, Sputum fcintillans Felt- 
fpatum 
• This has its name from its figure but 
fee ms to be of the fame fubfcance as the 
jafper. I have not however ranked them 
together, for want of true marks to difcin- 
guifn the different forts of the flinty tribe 
from one another. 
This kind is found, 
1. Sparry. 
a. White. 
h. Reddifh brown, occurs in the Swedilh 
and alfo in the foreign granites. 
c. Pale yellow. 
d. Green iih. 
This laft mentioned refembles very 
much the fchori or cockle-fpar, (Sedt. 
Ixxiii.) but is neither fo eafy to melt in 
the fire, nor of fo exad a figure. 
2. Crifliailifed. 
v/ith them in form of an earth, which perhaps we do not 
hnow in that Hate. It may be afked, Whether this earth will 
be dudile as clay, or rough to the touch as powder of bricks ? 
Perhaps Tripoly is produced in this manner. 
* i'he Germans and other nations call this fubftance 
Feld-fpat, that is feiid or vague fpar • a name very inadequate 
to its nature, as it touches no wife on the fparry clafs. J 
have therefoie, in my Lediures, given it the Engliih name of 
Rhombic Quartz, a name very figniheant, as the name quartz 
expreffes its clafs ; and the quality of it, of always breaking 
into angular (rhcmbic} fragments, is alfo exprelTed by the 
adjedlive pf rhombic. D. C. , 
f What Croniiedt means, that the feld-fpat has its name 
from its figure, is unhiteliigibie. D. C. 
A. In 
