H. W. Turner — Gold Ores of California. 471 



This would indicate that the feldspar of the dike rock is 

 also albite although not so pure as the secondary albite that 

 occurs in veins cutting the dike rock. 



The feldspathic lode of the Shaw mine is cut by little veins 

 of quartz, but judging from the specimens sent, these are not 

 very abundant, and do not seem to be connected with the depo- 

 sition of the gold. 



The quartz veins cut the veins of secondary albite showing that 

 they were formed later than the albite. In one specimen there 

 seemed to be an intermingling of quartz and albite, pointing 

 to contemporaneous deposition. But in thin section, the idio- 

 morphic albite crystals were plainly seen to be enclosed in the 

 quartz, as if there had been a little fissure, the walls of which 

 were coated with albite crystals and the open spaces in the 

 middle between the albite crystals later tilled in with quartz. 

 All of the material of the lode, except perhaps the quartz, 

 contains iron disulphide scattered through it in minute cubes, 

 and calcite in little rhombs and particles. 



Orofino gold mine. — One and a half miles northeast of 

 Mount Aigare in Eldorado county on the west side of Big 

 Canon creek is a dike of rock about 1500 feet long with a 

 nearly north and south strike but curving to the southwest at 

 the south end. This dike is much broken up, and re-cemented 

 into a breccia. One of the specimens of the dike collected 

 there by the writer in 1889 is a quartz-diorite, containing 

 specks of iron disulphide and calcite ; another specimen which 

 seemed to grade over into the diorite is composed of a plagio- 

 clase feldspar probably albite, calcite, and grains of iron disul- 

 phide, and strongly resembles in thin section the vein material 

 of the Shaw mine. This last specimen has a brecciated struc- 

 ture. It is auriferous and is the ore of the mine known as the 

 Orofino gold mine. The country rock of the mine is clay 

 slate, the same belt as at the Shaw mine, and is probably Car- 

 boniferous in age. 



The gold deposits of both the Shaw and the Orofino mines 

 are of such an unusual nature as to deserve further investiga- 

 tion. 



Petrels River mine. — One mile northwest of the town of 

 Mokelumne Hill in Calveras county on the north bank of the 

 Mokelumne river is a quartz mine, owned by Mr. R. W. 

 Petre. , There are here two quartz veins which have a north- 

 westerly strike and dip southwesterly about 80°. The veins 

 are very irregular in width opening out into lens-shaped bodies, 

 and quickly pinching out again. Mr. Petre stated that one 

 of these lenses contained $10,000 in gold, but that most of the 

 quartz was of low grade. The country rock of the mine is a 

 quartz-diorite. Some granite schistose material occurs along 



