| Show WHERE TELLURIDE ORES ARE FOUND prof jos luce in the news san diego cal continued from last issue As stated in the proceeding prece eding articles the telluride ores accompanied by the gold bearing copper ores occupy the lower front range in boulder county as a little higher up the gold ores have a monopoly in gilpin county still higher up in clear creek county are found the silver bearing ores whose associated minerals are galena blende blande and pyrite with a fair sprinkling of gray copper and ruby silver further up and in the main range are found the carbonate ores accompanied by bromide and chloride of silver the front range is deeply put cut by numerous craggy gulches and canyons in casing narrow and rapid creeks running from the west towards the the east carrying with them rich gold detritus forming bars and placers along the foothills before sinking under the alluvium of the colorado prairies the erosion of the walls of these canyons and gulches has exposed to view the different rocks and the of the country the exposed rocks are mostly gneiss and metamorphic then quart quartz porphyry slates and and granite the whole being reticulated by numerous dikes of of various ages and natures along the foothills this formation dips under the up upraised raised strata of the triadic red beds covered themselves by atlie jurassic the cretaceous beds and as said previously the whole overtopped over topped by the great lignite formation of colorado and the alluvium of the plains Ab according cording to professors F V hayden and lesquereux this lignite formation belongs to the eocene or lower tertiary while lieutenant G M wheeler and professor leconte ascribe it to the upper chalk beds of the cretaceous period the telluride veins to a regular system of fractures running northeast and southwest with a nearly vertical dip the walls are quite regular and occasional slick in sides due to lateral pressure are found always coated more or less with sulphides sulp hides and tell urides of great richness without attempting to describe all the tellurium minerals found in these veins we will name those most commonly met with in the mines of the belt native tellurium rarely pure 1 telluride of bismuth 2 telluride of nickel 3 telluride of lead 1 4 Kes site telluride of silver 5 telluride of gold 6 sylvanite telluride of gold and silver 7 Mull erite telluride of lead 1 8 telluride of gold and silver 9 telluride of mercury 10 ite telluride of lead gold silver then as minerals of alteration magno lite telluride of mercury telluride of iron the minerals numbered from 1 to 6 are found in great abundance the frequency of the others is indicated by their numbers native gold in nuggets scales and threads is often found accompanying the mineral in depth metallic sulphides sulp hides such as those of iron and copper galena blende occur frequently cinnabar and amalgam are also found the gangue orl or matrix of the ores is variable it is nib mostly s i aly formed formed by a compact flinty quartz colored by the metallic minerals of the veins sometimes the black coloration is due to very minute crystals of tell urides of lead bismuth etc it is often colored in yellowish green by variety of in which part of the vanadium has been replaced by the veins on sugarloaf Sugar loaf mountain contain a certain quantity of native bismuth and some carbonate of the same metal t nearer to the boundary of gilpin county large and beautiful crystals of pyrite and other nickel minerals pech blende etc are found but of all minerals the most welcome is fluor spar that abounds in the richest part of the veins A characteristic feature of the veins is their ribbon like appearance and regularity the small width of most of them is compensated pen sated by the great richness of their ore in some of these small veins the color of the quartz is occasionally of a reddish brown color which under a strong microscope shows the quartz impregnated with fine gold and crystals of sylvanite partly decomposed the most important mine of the county is the melvina its vein is a typical one and the sylvanite is the only telluride found the vein is formed of alternate zones of quartz feldspar and gneiss detached from the walls its ribbon like appearance is striking and the ores taken out and sent to the market are generally divided into three classes ranging from to per ton below these figures the ores have been first accumulated in dumps but today all these dumps have disappeared and surrendered their precious contents to the more economic methods of the modern met allergist A remarkable feature of the gold found in the placers fed by the creeks emerging from the front range is its fineness as compared with the california gold while the last is from 1 to fine the boulder county gold reaches from to in fineness the largest vein ever found was struck in the corning tunnel its width between the walls is from fourteen to fifteen feet but the mineral is low grade due to the presence of pyrites seven different veins were struck in the same tunnel all different as to their nature and the value of their ores however all were veins of telluride ores |
