360 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



of portions of complex twins of phillipsite. The crystals, which 

 reach 5 mm. in diameter, are intimately intergrown, poorly developed, 

 and complexly twinned, and no reliable crystallographic measure- 

 ments could be made. Optically the material seemed somewhat 

 variable in properties and a ground and screened sample was ac- 

 cordingly treated with heavy solutions. Two products were thus 

 obtained but these intergraded in specific gravity. 



The lightest product which appeared homogeneous under the 

 microscope was found to be biaxial positive with 2V small to medium, 

 dispersion r<v strong. The refractive indices are a= 1.492, /3= 1.494, 

 7=1.498, all±0.003 (variable). Sections perpendicular to an optic 

 axis show no extinction in white light. Many of the grains show a 

 confused grating structure. This purified sample was analyzed with 

 the following results : 



Analysis of chabazite (?) from Glenns Ferry 



(E. V. Shannon, analyst) 



Per cont 



Silica (Si0 2 4(3. 28- 



Alumina (A1 2 3 21. 52 



Lime (CaO) 8. 60 



Soda (Na 2 0) . 56 



Potash (K 2 0) 4. 52 



Water (H 2 0) above 110° C 14. 52 



Water (H 2 0) below 110° C 4. 28 



Total 100.28 



This analysis may be compared with some published analyses of 

 high potash chabazites or it agrees equally well with many analyses 

 of phillipsite. Neither the chemical, optical, nor crystallographic 

 data obtained are sufficient to definitely determine whether the 

 mineral is phillipsite or chabazite. Most of the crystals have the 

 appearance of chabazite, but more crystallographic data, based on 

 better specimens, is needed to finally settle the identity of this 

 zeolite. The heavy product from the heavy-solution separation con- 

 sists of the same material as the analyzed sample mixed with blades 

 of the thomsonite described below. 



ANALCITE (450) 



Hydrous soda-alumina silicate, approxi- Isometric, 



mating Na 2 O.Al 2 3 .4Si0 2 .2H 2 0. 



Analcite is a zeolite which is isometric in crystallization, although 

 optically it is biaxial. It has been found in Blaine and Custer Coun- 

 ties in Idaho. 



BLAINE COUNTY 



A specimen collected by D. F. Hewett from the Golden Bell mine, 

 which is near the head of the gulch which contains the Minnie Moore 

 mine near Bellevue in the Wood Kiver district, contains some anal- 



