CHARACTERISTICS OF THE ORE. 11 



total percentage of WO 3 may be as high as or higher than that in ores 

 which are easily and profitably worked. 



In the southwestern part of the field the narrower individual veins 

 are made up almost wholly of ferberite, which has grown from both 

 sides of the crevices and forms combs of small crystal** that coalesce 

 at their bases. The combs are of fairly uniform thickness, so that 

 although in the narrower crevices they may have met and grown 

 together, in the wider cracks they form bristling crusts of crystals on 

 each side. In places these crystals are clean and bright but generally 

 very small, from one to three thirty-seconds of an inch (1 to 2 milli- 

 meters) across. Most of the crystals are covered with a coating of 

 impure chalcedony, which in some specimens is mixed with opal and 

 in others contains much iron. The coating generally includes, small 

 crystals of ferberite, which are of course of a later generation than 

 those on the walls. Some vugs 3 or 4 inches across are entirely filled 

 with such a mixture. 



On the Nugget claim, 3J miles southeast of Nederland, the crusts of 

 nearly pure ferberite reach a thickness of more than an inch, and this 

 claim has produced the finest crystallized specimens of ferberite yet 

 found. In the veins of this claim, as in the others, most of the crys- 

 talline aggregates are covered with a siliceous mixture, which here 

 carries much brown iron oxide. The veins cut a moderately coarse 

 grained pegmatite and have so far produced only a small quantity of 

 ore. The Winnebago, an adjoining claim, has produced some small 

 specimens of crystallized ferberite from similar veins. 



In places the country rock instead of being sheeted is crushed into 

 smaller, more nearly equidimensional fragments, which may not be 

 over one-eighth inch (3 millimeters) in diameter. Ore in which frag- 

 ments of rock no larger than half an inch (13 millimeters) across 

 are embedded in ferberite is popularly known ^J/pejnujt" ore, from 

 its resemblance to peanut candy. (See PL I.) The fragments of the 

 breccia vary greatly in size (PL II), and where the fragments are larger 

 the breccia is characterized by vugs lined with ferberite crystals. 

 Both finely and coarsely brecciated ore is typical of the veins of the 

 district. Many of the veins have been opened several times., sathftt 

 the ferberite itself is brecciated. (See Pis. Ill and IV, .) 



In places the ferberite carries considerable manganese and grades 

 int < > wolframite. The mineral from Gordon Gulch carries almost 6 per 

 cent MnO (analysis 58, pp. 30-31 ) and wolframite occurs on the north 

 side of the field at Ward (analysis 49). The only other tungsten 

 mineral so far identified in the field is scheelite. which occu 



ral nearly 



quantity as a thin coating of octahedral nearly white rys 

 one thirty-second inch (1 millimeter) in thickness, over a fprn n^ far- 

 berite covering the walls of crevices in the Sugar Loaf district 

 northern-central part of the area. Vugs in ore from the Frigid Mining 



