CALOITIC VEINS OF ARARAT MOUNTAIN. 



103 



On the Reptile claim, above the Wingfield tunnel, an outcropping vein of this 

 material is beautifully banded, and consists of brown and white calcite and some 

 quartz (fig. 1-t)." Some assays of this are said to show a value as high as $20, all 

 in gold, but it is mostly barren. Several small veins near by are of the same 

 character. One of these distinctly shows quartz as a later deposit than calcite 

 (fig. 15). These veins have a general northerly trend, and the vein zone can be 

 followed all the way across the hill to the contact on the north, but no farther. 

 Each vein can be followed only a short distance, however, when it becomes con- 

 fused by reason of splitting, straggling, and thinning, while a lateral vein may 

 thicken up so as to become of predominating importance. 



At the contact between the white rhyolite plug and the glassy Tonopah rhyolite- 

 dacite, on the east side, 

 an 8-inch vein of banded 

 white and brown calcite 

 and siderite, cementing 

 a fissure in the white 

 rhyolite, was observed. 

 This has a strike of N. 

 10 W. and a dip of 70 

 to the east. 



On the oppo.site or 

 west side of the intru- 

 sive plug, near or at the 

 contact between it and 

 the later andesite, there 

 is a vein of beautifully 

 crustified crystalline cal- 

 cite, locally 20 feet 

 thick. The rhyolite on 

 one side of the vein has been silicified so as to form a pale-yellow jasper. 



It will be noted from PI. XIV that these veins, although their position and 

 trend are governed to a large extent by the contact, have a general north-south 

 trend independent of it. This indicates that the chief strain at the time the fissures 

 were formed was in a direction nearly at right angles to the longest axis of the 

 elliptical horizontal cross section of the volcanic plug. This north-south trend is at 

 right angles to the principal trend of the ore-bearing veins in the earlier andesite, 

 formed at an earlier epoch (fig. 12, p. 84). 



a Dr. W. F. Hillebrand kindly examined the dark-colored carbonate for the writer. He finds it essentially calcite, 

 with very small amounts of iron and manganese carbonates, a considerable amount of mechanically included hematite, 

 and some black manganese oxide. 



-iz$< 



3 feet 



FIG. 15. Vertical cross section oi outcropping tissure vein, 20 feet west of section 

 shown in fig. 14. 1. Calcite with angular rhyolite fragments; 2, quartz; 3, 



white rhyolite. 



