292 = Cross and Hillebrand—Cryolite from Colorado. 
but nothing observed is in conflict with the reference to the 
monoclinic system 
hemical investigation.—The formula deduced by Brandl* 
for prosopite, from the results of his analysis as here given :— 
Atomic values. 
F 35°01 1°842 
Al 23°37 0°853 
Ca 16°19 0-405 
Mg 0-11 0-004 
Na 0°33 0-014 
H.,0 12°41 0°689 
Loss as oxygen, 12°58 0786 
100°00 
is Ca¥’,, 2A](F, OH),. The whole of the water is assumed to 
be basic, entering with oxygen into the constitution of the 
mineral as hydroxyl, the latter replacing an equivalent amount 
of fluorine. In support of this assumption, Brand] mentions 
that no loss is perceptible below 260° C os 
In an earlier partial analysis, Scheerer (Pogg. Ann., ci, Pp. 
861) found 
Al 22-77, Ca 1641, H,O 15°50 
* Ann. de Chem., ccxiii, p. 13. 
