A. IT. Chester — Krennerite from Colorado. 375 



to ordinary andesites, but chemically they stand between the 

 andesites and the trachytes. They are higher in alkalies than 

 the andesites, the potash is generally in excess of the soda, 

 and, in the particular rocks described, is present chiefly in the 

 unindividualized glass, where no biotite is present. 



Rocks of this intermediate chemical composition are fairly 

 widespread, but characterized by considerable mineralogical 

 diversity. The name latite is proposed as a convenient designa- 

 tion for this entire group of effusive rocks, standing chemically 

 about midway between the andesites and trachytes, and corre- 

 sponding to the plutonic monzonites of Brogger and possibly 

 to some of the dike banakites of Iddings. 



Washington, D. C, March, 1898. 



Art. XLYI. — On Krennerite, from Cripple Creek, Colorado; 

 by Albert H. Chester. 



The writer recently received from Messrs. George L. 

 English & Co. a specimen from the Independence Mine at 

 Cripple Creek, Colorado, which shows a number of very dis- 

 tinct crystals of krennerite, a mineral not previously identi- 

 fied from this country. This species was first noticed among 

 minerals from Nagyag in Hungary, and described by Krenner* 

 in 1877, under the name bunsenin. In the same year vom 

 Rathf called it Krennerite after its discoverer. . It is an exceed- 

 ingly rare mineral and has heretofore been found only at the 

 original locality. 



The mineral from Cripple Creek occurs in brilliant crystals 

 of a pale yellowish-bronze color, but tin-white on cleavage 

 faces. The largest of these crystals, of which there were 

 originally about thirty on the specimen, are about 2 ,nm in length 

 and the same in breadth, and they are at once recognized as 

 belonging to the orthorhombic system, showing prismatic faces 

 deeply striated, pinacoids and domes, and resembling some 

 forms of arsenopyrite. Some of the crystals show a perfect 

 basal cleavage. The crystallographic examination has been 

 made by Prof. S. L. Penfield, and his results are given later. 

 The mineral is very brittle and has a hardness of about 2*5. 

 Heated on charcoal it decrepitates violently, and fuses easily, 

 burning with the characteristic bluish-green flame of tellurium, 

 and coating the coal with its oxide. A globule of seemingly 

 pure gold finally results. It has therefore the characteristics 



* 1877, Term. Fiiz , Pt. 1. 

 f 1877, Ak. Ber. Mouat., 292. 



