GUIDE TO Till: MINBBALOGIC COLLECTIONS ll'T 



VARIETIES 



Selenite. A colorless transparent variety usually in distinct 

 i rystals or broad folia. 



Fibrous. A coarse or fine fibrous variety, fcranslucenl and 

 silky in luster. 



Alabaster. A compact, fine grained gypsum much used for 

 carved objects. 



Rock gypsum. An earthy dull colored variety often contain- 

 ing clay, calcium carbonate or silica ;is an impurity. 



Extensive deposits of gypsum have resulted from the evapora- 

 tion and concentration of ancient seas and landlocked waters. 

 Gypsum is also produced by volcanic action and from tin- decom- 

 position of limestone by sulfuric acid. In New York gypsum is 

 found throughout the rocks of the Salina group in considerable 

 quantities associated with halite. Deposits also occur in Ohio, 

 Illinois, Virginia, Tennessee, Kansas and Arkansas and to a 

 considerable extent in Nova Scotia. 



Gypsum is burned and ground for plaster of paris and when 

 -round from the raw material is of considerable value as a 

 fertilizer. Alabaster and. to some extent, satin spar are used 

 for carved ornamental objects. 



Epsomite (epsom salt) MgSO r 7H.0 



Epsomite is a hydrous magnesium sulfate, n is usually 



found in white botryoidal masses and delicately fibrous crusts 

 and is characterized by its bitter saline taste. 



Alunite (alum stone) K(A10),(S0,),-r3H,0 

 Aluuile is a hydrous sulfate of aluminium and potassium. 



It crystallizes in rhombohedrons closely resembling cubes. It 

 also occurs in massive forms of fibrous, granular or impalpable 

 structure. The color is generally white, often shading to gray- 

 ish Or reddish. The luster is vitreous to pearly. 



It occurs as seams in rocks of a trachytic character where it 



has been formed by the action id' sulfur dioxid and steam. It is 

 found in Kosila hills. < !ol. 



Alunite is used in the production of alum. 



