BNDLicH.] SAN JUAN MINES. 233 



prospectiuof as well as the further developments of the veins already 

 claimed. On Mineral Point the main strike is northwest to southeast 

 approximately, although several lodes cross each other, and others 

 occur, striking from northeast to southwest. As a rule, the width be- 

 tween walls may be stated at 4 to 12 feet, but larger veins occur. The 

 ores mainly found are galenite, middle to fine grained, containing 

 silver, sphalerite, from light yellow translucent to the brown varieties, 

 pyrite, chalcopyrite, and fahlerz (brittle silver), which throughout that 

 region appears to be an antimonial tetrahedrite, containing mainly sul- 

 phur, antimony, copper, and silver, replacements being produced by 

 iron and zinc. About 8 to 13 per cent, of silver may be regarded as the 

 limits within which it occurs in the pure mineral. This variety of 

 tetrahedrite has been distinguished as freibergite. 



The gangue appears to be mainly quartz. As some of the locations 

 of that section, belonging to Eureka district, I would mention Dakota, 

 Mineral Point, Eed Cloud, Little Twinkle, Mastodon, Bond Mine, and 

 Equator. One of the lodes on Mineral Point shows a manganese de- 

 posit on the surface (psilomelane), while farther down galenite forms 

 the main body of the ore. 



In the Placer Gulch, Burrow's Park, Adam's Park, and at the head- 

 waters of the Uncompahgre a number of lodes have also been located, 

 showing ore similar to those from Mineral Point and the immediate 

 vicinity. 



Upon the mines of Eureka Gulch no data could be obtained, owing to 

 a lack of time. 



Descending Cunningham Gulch, Galena Mountain is found on the right 

 hand, while Kendall Mountain is on the left. Near the head of the gulch 

 and on either side lodes have been located, and worked to some extent. 

 As above mentioned, the lower portions of the caiion consist of chloritic 

 schist, stratified, but standing on edge ; while the upper portions are formed 

 by the bluish volcanic rocks of l^o. 4. Several well-defined veins extend 

 from the lower to the upper, and, as I was informed, the continuation 

 had in two instances been traced beyond the ridge of the mountain to 

 the other side. A considerable amount of debris precludes the possi- 

 bility of following the veins to the bottom of the gulch, but, judging from 

 analogy, they may be considered to extend some distance farther down 

 beyond the point where at present they can be seen. This caiion now 

 being one of the main routes of ingress and egress to and from How- 

 ardsviUe, prospectors have been attracted more particularly to the 

 study of its vicinity, and ore has been obtained from several veins, 

 yielding, even when taken from the surface, a comparatively large 

 percentage of silver. 



Near the head of the gulch, on the left hand descending, the 



HIGHLAND MARY 



is located. It has a strike of north 68° west, and vertical dip.* Between 

 walls the gangue and'ore average from 4 to 5 feet. To the northwest the 

 extension of the vein has been found and claimed as the "Robert Bruce." 

 Toward the gulch the Highland Mary runs through the horizontally 

 stratified trachytes of No. 4, corresponding in character to that de- 

 scribed from station 14, of a bluish color. The line of junction between 

 this volcanic rock and the underlying metamorphics is well marked and 

 readily distinguishable. Without showing any change in course or width, 



* The dips are given as the variation from the vertical. 



