ART. 13 



MINERALS FEOM SOUTHERN UTAH SHANNON 



9 



be a hydrous magnesium sulphate free from ammonia, potash, 

 chlorine, and carbon dioxide. Under the microscope this was seen 

 to consist of small equidimensional euhedral crystals loosely aggre- 

 gated. These lie on faces either perpendicular to V or to an optic 

 axis. They are biaxial and negative with 2E medium small, dis- 

 persion weak. The indices of refraction are a= 1.430, )8^ 1.455, 

 <p = 1.4G0. These optical properties indicate that this material at the 

 time of examination was also, epsomite and this also has altered 

 completel}'^ and the specimen has fallen to pieces. It was not 

 analyzed. 



Fig. 1. — Celestite crystal. Panguitch, Utah 



Celestite does not occur immediately associated with the epsomite 

 and ammonia bearing sulphates but is a constituent of separate 

 specimens made up of celestite and paligorskite in friable red sand- 

 stone. Some of the specimens consist almost entirely of massive- 

 granular celestite with very little paligorskite and others are pali- 

 gorskite free from celestite. The best specimens are of a vein in 

 sandstone which has an open cellular filling of mixed paligorskite 

 and celestite. The celestite is later than the paligorskite and some 

 of the smaller celestite crystals which are supported by the fibers 

 are doubly terminated. They range from 1 millimeter to 2 centi- 

 meters in length although the larger ones show parallel growth 

 and are curved and imperfect. The smaller transparent and more 

 perfect crj^stals have the habit shown in figure 1 and are tabular 

 from the development of A'ery flat domes, and elongated parallel to 

 the h axis. The larger and less perfect crystals are similar but the 



