24 Sypney H. BALL: 
rying, according to TATLER and others, from 0.41 to 0.7 % silver and 
the chalcopyrite is slightly auriferous. 
Quartz is widely distributed within the cryolite and usually has 
good or partial crystal forms. Against siderite, the quartz usually has 
well developed crystal faces. The other impurities, as a rule, occur 
closely associated with 
siderite, although they 
are also in certain lo- 
calities disseminated 
within the cryolite it- 
self as crystals, usually 
from 0.6—1.25 cm (/, 
to 1/, inch) in diameter. 
In the impure aggre- 
gates chalcopyrite usu- 
ally forms a core within 
blende or galena cry- 
stals, and against the 
latter minerals siderite 
usually, although not 
always, has its own 
form (Fig. 9). The order 
ofcrystallization within 
the main mass would 
appear to have been 
quartz, siderite and 
chalcopyrite, followed 
by blende and galena, 
and lastly by cryolite. 
The period of crystal- 
lization of the first two 
Fig. 11. Quartz—microcline—cryolite—galena— groups, however, clear- 
pegmatite. Natural size. ly overlapped, and, in 
Q = Quartz. M = Microcline. C = Cryolite. G = Galena. instances, galena is 
enclosed in siderite. 
In the main mass of the cryolite are transparent masses of cryo- 
lithionite as first noted by N. У. Ussing") in 1903. It is not only massive 
but also occurs in rhomboidal dodecahedra up to 18 cm (7 inches) in 
diameter. Containing, as it does, 11.4 % lithium, it is the richest lithium 
mineral in the world. 
1) Oversigt over det kongelige Danske Videnskabernes Selskabs Forhandlinger 
1904 p. 3—12. 
