Genth and Penfield — Contributions to Mineralogy. 385 



nonnced prismatic habit. They are iron-black. Sp. gr. 

 4 -249. "The analysis gave, after deducting - 7 per cent of 

 quartz : 



Sn0 2 1-40 



Ti0 2 . - 91-96 



FeO 6-68 



100-04 



5. Quartz resulting from the alteration of the flesh-colored ortho- 

 clase of W. Cheyenne Canon. 



The orthoclase crystals become rounded and in their decom- 

 position leave cavities which are partially filled with grayish- 

 white porous and cavernous coatings either directly upon the 

 orthoclase or with some space between, filled with earthy 

 limonite. The pure grayish or slightly greenish white material 

 shows a cry ptocrystalline structure, dull or with a faint vitreous 

 luster. BL.=8; Sp. gr. =2-552. 



In appearance it somewhat resembles some varieties of the 

 so-called damourite. 



The analysis gave : 



Ignition.. 0'95 



Si0 2 96-63 



A1 2 3 0-93 



Fe 2 3 __ 0-85 



Na 2 ' trace 



KO 0-46 



99-82 



from which it is evident that it is cpiartz, slightly contami- 

 nated with orthoclase. 



In the same orthoclase is a mineral in very tine and minute 

 needle-shaped crystals of a greenish yellow color which could 

 not be identified for want of material. 



6. Danalite. 



Among some specimens from "W". Cheyenne Canon, El Paso 

 County, Colorado, which were given to me for identification 

 by Messrs. Geo. L. English & Co. were two fragments, one of a 

 crystal 15 X 17 mm in size, the other not showing any crystalline 

 form. Both were discolored by iron and manganese oxides 

 and were found to be an interesting variety of danalite. 



