502 W. E. Ford— Mineral Notes. 



Art. XLIIL— Mineral Notes; by W. E. Ford. 

 I. Occurrence of Chalcophanite at Zeadville, Colorado. 



The Brush Mineral Collection recently acquired through 

 the gift of Dr. F. B. Laney several additional specimens of the 

 zinc-manganese oxide, hetserolite, from the Wolftone mine, 

 Leadville, Colorado. This occurrence was recently described 

 in an article from this laboratory.* The heteerolite on the 

 specimens showed no new features worthy of note, but asso- 

 ciated with it was a crystallized mineral which on examination 

 proved to be the rare species, chalcophanite, (Mn, Zn)0.2Mn0 2 . 

 2H 2 0. This mineral has been previously observed only at 

 Sterling Hill, Ogdensburg, N. J. It occurred on the Lead- 

 ville specimens as crusts of minute hexagonal plates covering 

 the botryoidal surfaces of the hetserolite or lining the cavities 

 in the specimen. No crystal faces were observed other than 

 the basal plane. The color of the mineral was a blue-black to 

 an iron-black. Its streak was chocolate-brown. Very thin 

 plates under the microscope showed a dark brown color. 

 These were sufficiently transparent in one or two cases to give 

 a distinct uniaxial interference cross. The mineral proved to 

 be optically negative. While the chalcophanite from the 

 original locality is stated to be opaque to light, an examination 

 of it under the microscope showed that on very thin edges it 

 also had a dark brown color. The Leadville material when 

 heated in the closed tube yields water and its crystals exfoliate 

 somewhat and change to a bronze color. It gives reactions 

 for manganese and zinc. These tests leave no doubt as to the 

 identity of the mineral. 



II. The Index of Refraction of Manganosite. 



Recently it became desirable in the course of another inves- 

 tigation to know the index of refraction of manganosite, the 

 manganese oxide, MnO, this having apparently never been 

 determined. Some specimens of the mineral from Franklin, 

 N. J., were in the Brush Mineral Collection, having been pre- 

 sented by Prof. Charles Palache. A small fragment of the 

 pure mineral was secured from which a prism could be ground. 

 The mineral is colored a deep green and is only transparent on 

 quite thin edges, but after several attempts a small angle prism 

 was obtained through which light could be transmitted. 

 When this prism was illuminated on the refractometer with 

 white light it unexpectedly gave two distinct images of the 

 refracted ray, one colored red and the other green, instead of 



* This Journal, xxxv, 600, 1913. 



