472 II. IF. Turner — Gold Ores of California. 



the main veins. A microscopic examination of this shows 

 that it is practically a chlorite-schist. It is composed of a 

 schistose aggregate of minute grains of feldspar, with much 

 chlorite, and calcite. This schist is doubtless an attrition 

 product, formed by movement along the walls of the vein. 

 In one part of the vein there is a good deal of a hard white 

 materia], which the microscope shows to be largely feldspar, 

 presumably albite. The feldspar occurs in nnstriated inter- 

 locking grains with occasional twinned prisms. There is a 

 good deal of calcite, pyrite, and mnscovite, and foils of 

 a green chloritic mineral. In the quartz-diorite country rock 

 near the vein are a number of rounded bodies of calcite, some 

 three feet in diameter. This calcite was doubtless deposited 

 in pre-existing cavities. 



Gold with harite. — Mr. ~W. Lindgren* has described an in- 

 teresting deposit at Pine Hill, Gala. In a zone of decomposed 

 and kaolinized diabase are irregular veins or seams of barite 

 with which gold is associated. Other similar associations are 

 noted. 



Mr. Wirt Tassin of the U. S. National Museum kindly called 

 my attention to a paper by Henry Louisf on the mode of 

 occurrence of gold. Mr. Louis gives a list of 77 species of 

 minerals, some of which however are formed from the decom- 

 position of previously existing minerals that are found in gold 

 veins. Only one feldspar is noted, orthoclase from Colorado. 

 The exact locality is not given. The author further says that 

 while iron pyrite is an almost universal constituent of gold 

 quartz veins, marcasite seems never to occur; and in conclusion 

 suggests that the gold and quartz have been simultaneously de- 

 posited in veins from alkaline solutions. 



Gold in calcite. — The Yellowstone mine at Bear valley, 

 Mariposa county, is in diabase. The course of the vein is 

 about W. 20° S. The ore occurs in the altered diabase broken 

 up along the vein and re-cemented with quartz and calcite. A 

 specimen of the ore presented by the superintendent, Mr. 

 McDonald, to the National Museum shows spots of free gold 

 at numerous points associated with white quartz and calcite. 

 According to Mr. Hall, the former owner, in the upper work- 

 ings a good deal of the gold occurred in calcite. 



In the collection of the U. S. National Museum there is a 

 specimen of calcite in which are threads of native gold. This 

 was collected by Dr. W. H. Melville from the Bannock mine, 

 Montana. 



Gold with qxiartz in rhyolite. — One mile east of Onion 

 valley in Plumas count}', California, is a dike of rhyolite in 



*This Journal, vol. xliv, 1892, pp. 92-96. 



f Mineralogical Magazine, vol. x, 1893, pp. 241-247. 



