TSCHEEMAK FELSPAKS. 19 



Anorthite €a, Al^ Al, Si^ 0,g 



Albite Na^ AI3 SiJ Si, O.^ 



Adularia K^ Al/Si/Si, O^g 



Hyalophane Ba^ Al^ Alg Si^ Ojg 



Danbiirite Cag B2 B Si^ O^^. 



In regard to the genetic relations of the Felspars, they may 

 be classified as follows: — (1) occurring in freely formed crystals 

 (" Drusy" of Tschermak) ; (2) occurring in rocks of the Basalt 

 and Trachyte families ("Glassy" of Tschermak); and, (3) occur- 

 ring in other rocks in imperfect crystals or as compact masses 

 (" Compact " of Tschermak.) If, therefore, we place the compact 

 transition-forms between Adularia and Albite with Orthoclase, and 

 the glassy with Sanidine, — and, again, collect the passage-varieties 

 between Albite and Anorthite under the head of Plagioclase, and 

 the glassy under that of Microtine, — we shall have the following 

 scheme, showing the relations of these Felspars : — 

 Compact : Orthoclase. Plagioclase. 



Drusy : Adularia. Albite. Anorthite. 



Glassy : Sanidine. Microtine. 



The following Table, somewhat abridged from the origiaal, will ex- 

 hibitmoreclearly theauthor'sclassification of the Felspars,and his view 

 of the manner in which the different varieties pass into one another : — 



A. POTASH-FELSPAKS. 



1. Adtjlaeia Seeies. Potash 13 to 16 per cent. 



Drusy. Adularia, Pini ; Valencianite, Paradoxite, BreiL; Rhy- 

 acolite, Bose. 



Compact. Orthoclase, Breit,, in part ; Pegmatolite, Breit., in 

 part ; Microcline, Breit., in part, from Arendal ; Murchi- 

 sonite. Levy ; Weissigite, Jentzscli ; ChesterHte, Booth. 



Glassy. Sanidine, Nose, in part, from Rockeskyll. 



2. Amazonite Seeies. Potash 10 to 13 per cent. 



Compact. Amazon Stone, Breit.; Orthoclase and Pegmatolite, 



in part. 

 Glassy. Sanidine, in part (from Drachenfels andPerlenhardt). 



3. Peethite Seeies. Potash 7 to 10 per cent. 



Compact. Perthite, Thomson; Orthoclase, Pegmatolite, and 



Microcline, in part. 

 Glassy. Sanidine, in part. 



4. LoxocLASE Seeies. Potash 4 to 7 per cent. 

 Compact. Loxoclase, Breit.; Orthoclase, in part. 



B. SODA-FELSPAES. 



5. Albite Seeies. Soda 10 to 12 per cent. 



Drusy. Albite, G. Bose ; Pericline and Tetartinc, Breit. 

 Compact. Hj^Doselerite, Breit. ; Cleavelandite, BrooTce ; mixed 



Albite and Oligoclase, in part. 

 Glassy. Glassy Albite, PantcUarite, Ahicli. 



6. Oligoclase Seeies. Soda 8 to 10 per cent. 



Compact. Oligoclase, Breit. ; Sunstone, Scheerer ; Peristerite, 



Thomson ; Potash-oligoclase. 

 Glassy. Glassy Oligoclase, in part ; 'Kalncijovdiic, Forchhammer. 



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