REVIEIVS 199 



replaced by quartz, with fluorite, opaline silica, and kaolin, and con- 

 taining iron pyrites, and other sulphides, as well as various other min- 

 erals in limited quantities. 



Gold is the only metal which occurs in amounts of commercial 

 value. It is found normally as a telluride, or in a free state as a result 

 of the oxidation of the former. It is possible that some of the gold is 

 present as auriferous iron pyrites, but this must be quite rare as most 

 of the pyrites is valueless, and, as a rule in the camp, rock impregnated 

 with this mineral is considered of little significance. 



The free gold appears to be confined to zones of oxidation and 

 these frequently extend to depths of several hundred feet. It is gener- 

 ally in a very fine condition, but sometimes pieces up to a quarter of an 

 inch in size are found. It is usually rusty, but is otherwise remarkably 

 pure, with hardly any appreciable silver, even less than is found in the 

 telluride ores. The telluride of gold appears to be principally the 

 mineral calaverite, according to examinations made by Mr. W. F. Hil- 

 lebrand and Dr. S. L. Penfield ; but there is probably also some syl- 

 vanite and other compounds. 



Silver occurs only in very small quantities in most of the ores, 

 though at the Blue Bird and a few other mines it has been found in 

 considerable amounts, though not enough to make any showing in the 

 production of the camp. 



As an accessory mineral, galena has been found at a number of 

 places, but in small quantities. Some spahlerite occurs at a few 

 mines. Copper minerals are extremely rare, as are antimony com- 

 pounds also. Fluorite is common in many ores and is frequently 

 prominent by reason of the coloration it gives to the rocks. It is 

 sometimes intimately associated with quartz. Quartz is the most com- 

 mon secondary mineral. It is sometimes found in bodies and occurs also 

 as well-defined quartz veins, but more frequently it is homogeneously 

 disseminated throughout the ore or country rock, simply making them 

 harder. Such silicified rock is often confused with dikes by the 



mmers. 



Kaolin is common along fissures, resulting from decay of the feld- 

 spar of the eruptives ; it is either white or stained a brown or black 

 color. Calcite is not abundant and occurs lining the face of rocks or 

 filling small cavities. Gypsum, though not of frequent occurrence, is 

 found in bodies of some size in one mine. Barite and other minerals 

 also occur in small quantities. 



