272 = Cross and Hillebrand—Cryolite From Colorado. 
allied minerals occurring independently. The chemical anal- 
yses of the above article, which had been previously published 
apart, were made by J. Brandl* upon material selected and 
crystallographically examined by Professor Groth. By a crit- 
ical review of the existing literature, and by renewed investi- 
gations in doubtful cases, it was hoped to clear away the 
uncertainty which had hung about some of the members of the 
group, and as the available material was, for the most part, far 
better than had been examined before, it was possible to obtain 
very satisfactory results. 
In the present paper, frequent referénce will necessarily be 
made to the results of Messrs. Groth and Brandl. ing to 
better material, we are in some cases able to give new or sup- 
‘plementary data, and only in one instance, namely, in regard to 
the composition of pachnolite, is there any discrepancy between 
our results and those contained in*the articles above cited. 
a part of the Archean formation. A specimen collected near 
The cryolite locality lies on the southeast border of the ex- 
tensive district within which Amazon stone and its associated 
mi ls are so abundantly found in cavities in the granite. 
In the immediate vicinity astrophyllite and associated zirco 
occur in granitic veins, and also, as does the arfvedsonite, 1D 
veins of white quartz. : 
The minerals to be described occur in two veins of massive 
white quartz, and in each case they were discovered by pros- 
pee e two veins are scarcely more than one-third of a 
* J. Brandl, Sitzungsbericht der kénigl. bayr. Akademie der Wissenschaften 
zu Miinchen, 1882, p. 118, and Annalen der Chemie, cexiii, p. 1. 
