20 Bulletin of Laboratories of Denison University, ivoi. xii 



In the aplite there is an access of AI2 O3 after deducting 

 the amount required of the feldspathic constituent of . 0059 mole- 

 cules corresponding by weight to o. 6 per cent. , which is probably 

 combined as mica. From the above calculations the ratio of 

 soda feldspar to lime feldspar is 9:1 in the case of aplite and 

 17: I in the case of the granite, corresponding to lime-bearing 

 albite of Abo An, and Abi^An, respectively, when the albite 

 and anorthite molecules are combined to form soda-lime plagio- 

 clase. The potash feldspar in both the aplite and granite is 

 part orthoclase and part microcline. According to the calcula- 

 tions the relative abundance of the constituents in the aplite 

 may be expressed as follows : 01igoclase> quartz>- orthoclase 

 and microcHne>" muscovite. In the case of the granite the 

 potash feldspars are slightly in excess of the quartz, otherwise 

 the order of relative abundance of the constituents is the same 

 as for the aplite. 



I and II. Potash aplites. Described by H. W. Turner, JoUR. Geol. 

 1899, Vol. VII, p. 160; also Seventeenth Ann. Kept. U. S. Geol. Sm-v., p. 521. 

 W. F. Ilillebrand, analyst. 



Ill and IV. Soda aplites. Described by II. W. Turner, Jour. Gkol., 

 1899, Vol. VII, p. 152. Ill, W. F. Hillebrand, analyst. IV, II. N. Stokes, 

 analyst. 



V. Aplite. Described by H. S. Washington, Jour. Geoi.., 1899, ^'°^- 

 VII. p. 107. H. S. Washington, analyst. 



VI. Aplite. Stone Mountain, Georgia. Thomas L. Watson, analyst. 



