THE COLLECTION OF MINERALS 
ite and Rhodochrosite specimens furnish a long display of forms 
and colors (Desk Cases 8-10, Wall Cases I, J, K, QO). 
The Silicates embrace the larger number of mineral species 
and are the essential components of the crystalline rocks. They 
are unions of basic elements (the oxides of various metals) with 
the several forms of silicic acid. The group is subdivided into 
AZURITE FROM BISBEE, ARIZONA 
two sections: the Anhydrous and the Hydrous Silicates, and 
these again are broken up into smaller groups based upon simi- 
larity of their members to one another in regard to composition, 
crystallization and optical qualities. Among the Silicates there 
are several well-marked and compact groups, such as the Feld- 
spars, the Pyroxenes, the Amphiboles, the Garnets, the Sodalites 
and the Scapolites. 
— 
“WW 
