'C.NS' 
A SYSTEM OF 
^46 
h Blackifh grey, from Lerwik at Helk- 
fors in Weftmaniand, and from Cq^ 
logne in Germany. 
Cl Light grey, from Hellefors in Weft« 
manland. 
f?. Black. The table flate, or that kind 
ufed for large tables and for fchool- 
Bates. 
The naked eye, and the magnify- 
ing glafs much better, difcovers the 
micaceous particles in this kind to be 
as it were twilled in one another ; forhe 
clay feems likewife to enter into the 
compofition : However, it cannot yet 
be certainly aflerted that it is real 
mica which has that appearance in 
this kind. 
Of very minute and clofely combined 
particles, Cos partkulis conftans inipalpa’^. 
bilibus durus. The Turky ftone. 
This is of an olive colour, and feems 
to be the fined mixture of the firfi: Ipe- 
cies of this genus. It is found in loofe 
ftones at Biorkfkoginas in the parifh of 
Hellefors in Weftmaniand, though not 
perfe6lly free from crofs veins of quartz, 
which always are in the furface of the 
rock, and fpoil the whetftones. It is 
alfo faid tq be found in Tellemarken iq 
Norway. The beft of this fort come 
from the Levant, and are pretty dean 
The whetftone kinds, wheq they fplit 
eafily, and in thin plates, are very fit to 
cover houfes with, though moft of thern 
^re.qot pfed for that purpofe. 
SECT. 
