1892.] Mineralogy and Petrography. 615 
and have the macro-zone more highly developed than the brachy-zone. 
They show clearly that Groth is correct in regarding the mineral as 
isomorphous with amplectite, scleroclase and zincenite. The axial 
ratio, calculated from pyramidal faces that gave good reflections, is 
a@:b:c¢ = 5283: 1: .6234. The little-known members of the 
mesotype group on the Puy-de-Dém have recently been described by 
Gonnard' in some detail as regards localities. An analysis of the nat- 
rolite from the Puy-de-Maman yielded: SiO, = 48.03; AI,O, = 
26.68; Na,O = 15.61; H,O = 9.62; and that of the Tour de Gev- 
illat gave: SiO, = 47.88; Al,O, = 26.12; Na,O = 15.63; CaO = 
: The same author’ has made a crystallographic 
study of the hadties of the Puy-de-Dém. All crystals of this substance 
are beautifully modified but none show new forms. A peculiarly hab- 
ited aragonite from the Neussargnes Tunnel, Cantal, containsthe new 
forms Pz% and $P. The investigation of the nature of the nitro- 
gen Gindi in uraninite, promised some time ago, has been continued 
by Hillebrand‘ without, however, very great success. The most care- 
ful analyses of specimens from Glastonbury, Ct., and from Arendal, 
Norway, yield respectively : 
UO, UO, ThO, ete. PhO CaO HO N Fe,0, er at T sg 
23.03 59.93 11.10 3.08 IF .43 241 .29 
26.80 44.18 13.87 10.95 .61 undet. 1.24 .24 » = 
The principal result of the analyses is to the effect that all uraninite 
contains more or less nitrogen, sometimes amounting to as much as 
24%. The condition in which the element exists is unknown, but it is 
probably different from any hitherto observed in the mineral kingdom. 
Another result indicated is that the formulas that have been accepted 
as expressing the composition of the mineral do not do so. Specimens 
from many of the classical localities have been analyzed, and in nearly 
every case errors have been detected in the original analyses. The 
author concludes that while uraninite in general contains the same 
constituents, it varies widely in composition, and its physical character- 
„istics are often as distinct as are the chemical differences.——The 
keramohalite from Pico de Teyde, in the Canary Isles, is in little imper- 
fectly developed crystals imbedded in a yellowish white hygroscopic 
‘Bull. Soc. Franç. d. Min., 1891, xiv, p. 165. 
*Ib., xiv, p: 174. 
3Ib., xiv, p. 183. 
*Bull. U. S. Geol. Survey, No. 78, p. 43. 
