426 l\irner — Rocks and Minerals from California. 



as ordinarily is found in granitic rocks. It may be brookite, 

 but as before noted, occurs in somewhat rounded forms and 

 not in the small tabular crystals said to be characteristic of 

 brookite. Possibly the mineral is rutile. 



On p. 425 is given an analysis of the alunite by Mr. William 

 Valentine. It is probable that the titanic oxide in this analysis 

 was obtained from some of the minute grains of the titanium 

 mineral above noted. As the material was sensibly pure the 

 analysis may be regarded as representing its composition after 

 deducting the titanic oxide. 



Alunite has not been previously found in California so far as 

 known. 



4. Zircons from Gravels. 



Sometime since Mr. J. A. Edman of Meadow Valley, Cali- 

 fornia, transmitted to the writer some heavy sands from gravel 

 washings in California. One sample of these sands was com- 

 posed largely of zircon-like crystals. The material came from 

 a surface placer in Eagle Gulch near Edmanton about 4*5 kilo- 

 meters southwest of Meadow Valley, Plumas County. 



To make certain the character of these crystals some of the 

 sand was digested on a water-bath with IIP and H 2 S0 4 con- 

 centrated for about two days. The residue was then washed 

 and digested in HC1 and water, again washed and digested in 

 water alone to get rid of the dissolved material. The residue 

 consisted chiefly of the zircon-like crystals with a few black 

 grains, and a few specks of gold. Some of this residue was 

 powdered and mixed with Na 2 C0 3 and fused at a white heat in 

 a little platinum crucible for five minutes. The culot was then 

 washed in water. After the soluble material was removed 

 there remained very abundant minute hexagonal crystals sup 

 posed to be Zr0 2 . 



Some of the zircon crystals and the Zr0 2 ? were sent to 

 Prof. S. L. Penfield of the Sheffield Scientific School, who 

 kindly examined them and wrote that " the zircon crystals 

 resemble ones which I have seen associated with gold from 

 North Carolina. The forms are not unusual, 100, 110, 111, 

 311, and possibly 101. The hexagonal plates (referring to the 

 crystals obtained by fusion with Na 2 C0 3 ) resemble those I have 

 met in testing for zirconia. I do not consider the reaction a 

 very delicate one. The black grains may be chromite or some 

 spinel mineral which would resist treatment with acids." 



5. Molybdenite. 



On the southeast slope of Mt. Hoffmann in the Yosemite 

 National Park, at an altitude of about 9500 feet, is a lens com- 

 posed of garnet, epidote, quartz and calcite. This lies in a 

 narrow strip of gneissic rock at the contact with the granitic 

 mass that lies just east. Possibly it represents a metamor- 



