Turner — Rocks and Minerals from California. 427 



phosed limestone mass. In some specimens (No. 2176 S. N.) 

 of the material bright specks of a sulphide were noted. This 

 mineral was determined by Mr. William Valentine as molyb- 

 denite. 



About three miles north of west from Tower Peak in Tuo- 

 lumne County is a considerable mass of quartzite, marble and 

 black fine-grained gneiss. At the edge of the coarsely crystal- 

 lized white marble, which has a width of about 400 feet, is a 

 white schistose pyroxenic rock. Granitic rocks and quartz 

 veins cut both the marble and the schist. The microscope 

 examination of the granitic dikes showed them to be quartz- 

 diorites containing primary augite and titanite. An excavation 

 had been made on one of the quartz veins at the contact of the 

 marble and schist. No doubt it was regarded as a gold- or 

 silver-bearing lode. This vein contains a large amount of 

 green epidote, garnet and zinc blende and a bright bluish 

 metallic sulphide. This bluish sulphide was determined by 

 Mr. Steiger and afterwards Mr. Valentine as molybdenite. 



From a quartz vein in the granite on the south side of Knight 

 Creek, northeast of Columbia in Tuolumne County, some 

 specimens of quartz were collected by myself some years ago. 

 The rock containing the vein is of a type called granodiorite in 

 the Gold Belt folios. Molybdenite was found in these speci- 

 mens. The quartz prospect was called the Dorsey claim, but 

 should not be confused with a mine of the same name which has 

 more recently been developed on the ridge north of Knight 

 Creek. 



6. Tellurium, Selenium and Nickel in Gold Ores. 



The presence of tellurium in gold ores, especially in Cala- 

 veras and Tuolumne Counties, California, has been known for 

 many years. In some mines, as the Bonanza at Sonora, tel- 

 lurides are very abundant. The following new localities are 

 given on the authority of Mr. W. J. Sharwood* of the Uni- 

 versity of California. 



Tellurium and selenium were found in a mine on the Mother 

 Lode near Table Mountain in Tuolumne County. The selenium 

 was obtained as a red sublimate by heating some live or ten 

 grams in a glass tube. The tellurium was detected in occa- 

 sional specks by the sulphuric acid test applied to the powder 

 spread over the surface of a shallow porcelain dish. Con- 

 centrated sulphides from the same mine were found to con- 

 tain 1*5 per cent of nickel. The sulphides contain so much 

 MgC0 3 as to be difficult of chlorination. 



Mr. Sharwood also found tellurium minerals in isolated 

 specks with pyrite, etc., in quartz from the Keltz mine near 



* Communication by letter. 



