1 873.] Colorado Gold Mines. 15 



to the miner from 60 to 80 dollars a ton. The copper pyrites 

 carries most gold, and the fine-grained iron pyrites more 

 than the coarse, distinctly cubical, variety. The blende is 

 also associated with gold, and in some mines is the principal 

 vehicle of it, and the galena is invariably argentiferous. 

 This rich ore is always sold to the smelter, as it refuses to 

 give even as large a percentage of its gold to mercury as the 

 less concentrated ores of the body of the lode, where the 

 gold seems to be in a freer form. The second class ore, in 

 first class mines, will usually carry — 

 i'4 ozs. of gold, 

 5*6 ozs. of silver, 

 2*8 per cent of copper. 



It is always treated in stamp-mills where battery amal- 

 gamation is employed, and not over 33 per cent of the 

 above-named valuable constituents of the ore recovered.* 



The proportion of No. I. ore to No. II. ore rarely exceeds 

 one-tenth, and in most mines the quantity is too small to 

 make it worth while effecting any separation. 



The width of the lodes runs from 18 inches to 10 to 12 

 feet. An average width of the really productive lodes may 

 be set down at 3 feet, but they are all subject to contractions 

 and expansions, sometimes pinching to a mere thread, at 

 other times bulging into enormous bunches. Nor are any 

 of the lodes consistently productive. The mineralogical 

 portions are said to run in chimneys, which are interrupted 

 by streaks of poor or altogether barren rock. The term 

 " chimney" has been borrowed from California, but is not 

 applicable in Colorado, as the rich ground does not form 

 continuous vertical streaks, alternating with vertical streaks 

 of barren rock, but irregular regions of rich ore, merging 

 vertically and horizontally into poorer ground. The term 

 " cap" is applied indiscriminately to merely lean and alto- 

 gether barren ground. Of the latter there is comparatively 

 little ; and as the former includes all ore that will not yield 

 20 dollars of gold to the ton, much that is now left standing 

 in the mines, it is to be hoped, will some day or other be 

 removed with advantage. 



Unfortunately the mining in Gilpin County has been as 

 faulty as the milling, owing chiefly to two causes : — 



I. The subdivision of the lodes into very small claims. 



II. The failure of the companies very generally to work 

 their claims, — which has led to the mines being either let or 



* Mr. Albert Reichenecker, in the Berg-Hiittenmannische Zeitung, re- 

 produced in Raymond's Report on Mines and Mining for 1870, p. 360. 



