GUIDE TO THE MINEKALOGIC COLLECTIONS 



115 



Kaolin is of secondary origin resulting from a decomposition 

 of the feldspars and other silicates. It occurs associated with 

 the feldspars, corundum, topaz, etc. Notable deposits occur in 

 China, Belgium, France, Bavaria and Cornwall. In the United 

 States kaolin is mined in Florida, North Carolina, Delaware, 

 Pennsylvania, and in somewhat poorer quality in Ohio. New 

 Jersey, New York and other states. 



As a constituent of porcelain, chinaware, tiling and similar 

 products its importance is constantly increasing. 1 



Pyrophyllite (pencil stone) H 2 AL(SiO.,) 4 



Pyrophyllite is a basic aluminium silicate. 



It occurs in radiated, lamellar or fibrous masses, sometimes 

 compact and smooth, soft and soapy like talc (pi. 36j). The lus- 

 ter is pearly to dull and the color white, greenish, brownish or 

 yellow. 



The compact variety is present in some schistose rocks and 

 the foliated form often occurs associated with cyanite. Pyro- 

 phyllite is found in North Carolina, South Carolina and Georgia. 



It is extensively used for slate pencils. 



Chrysocolla CuSi0 3 +2H 2 



Chrysocolla is a hydrous copper silicate containing :J4.3^ 

 silica, copper oxid and 20.5$ water. It is often very 



impure. 



Chrysocolla is found in green to blue masses with an enamel- 

 like texture; sometimes botryoidal; incr listing or filling seams. 

 Impure varieties often occur in earthy masses, green or dull 

 brown in color. 



Jt occurs associated with other copper minerals specially in 

 the upper parts of veins and is to be found in most of the copper 

 producing regions. 



It is an ore of copper and is also used for imitation turquoise. 



Titano-silkutcs. Titanah 8 



Titanite (sphene) CaTiSiO, 



Titanite is a calcium titano-silicate often carrying iron in 

 varying amounts and sometimes manganese and yttrium. 



1 For an exhaustive treatise on this subject see N. Y. state mns. Bui. 35. 

 1900. 



