290 Cross and Hillebrand— Cryolite from Colorado. 
ular spaces in the quartz, and probably replace feldspar, for 
ey are also found on fissure planes as distinct secondary 
deposits. 
118° 80’, to 119° 80’. The thinnest leaves show distinct action 
on polarized light, and extinguish parallel to the diagonals of 
the rhomb. The thicker crystals are made up of many thin 
ones which are usually not perfectly coincident in position, and 
sometimes form more or less perfect rosettes, 
The mica occurs in masses or foliated upon fissure planes, and 
no crystals have been found. The kaolinite possesses the com- 
position I, and the mica II, as given below, The kaolinite 
contained a small amount of fluorite in almost microscopic erys- 
tals, the quantity being caleulated from the Ca found. 
if 
Bile sect Ne ee, 45-93 SiO, puwedo Oo 
AiOgi aun was a 39°66 MOge to oe 29°72 
2 3 ae Gf Feo0, aweenS eee ee aN 
MON gC rook eS 0°84 1a0 ae er 
— ra 8 NOt lates er artie atin 
100°19 gad & Eulerian Car ese 8°33 
Va,0 roe O'OU 
1 Oy fuerte eee ey : £39 
99°31* 
Adjoining the quartz is usually an irregular zone of purplish 
or greenish fluorite, and next to this a rather coarsely granular 
* The presence or absence of fluorine was not ascertained. 
