Show WHERE ORES ARE FOUND prof jos luce in the news san diego cl cal continued from last issue the great importance of the researches made by the learned geologist john K hallowell whose patient and systematic observations ions have brought light upon the geological formation of the telluride belts give to his monograph a great usefulness for this reason it is in his own clear and comprehensive language that we will present its conclusions to the readers of the news who will better understand and appreciate the extent and thoroughness of his contributions to science he wrote in his monograph at a time when the system of elevations known as the rocky mountains had no existence the space now occupied by them was an ocean of vast extent but dotted here and there by islands of primitive granite the earliest or oldest rock known around these islands sedimentary rocks were being formed which were of varied thickness and extent and which afterwards by pressure and heat became metamorphosed such was the condition of the granite mountains gold hill and big horn just east of it in the olden age this granite rant island shoaled off from twenty to awen ty five miles south both on the east and west sides of the primitive formation heavy beds of sedimentary rocks afterwards metamorphosed were deposited gradually filling the ocean bed to a level when on the southern southe rn part of this island they overlaid it many feet in thickness the rock on the east side only came as fat far as boulder creek north of that and east of the mountains named there was none As this ocean gradually allowed swallowed sh on the metamorphic rocks was deposited the bedim sediment ent that afterwards made the cretaceous rocks of the plains and foothills at this place or island on the east side a few hundred feet only of this age of sedimentary rocks were laid directly upon primitive granite the other formations are entirely wanting at this time we have a shallow marshy sea with granite islands showing a small distance above the water level abundance of vegetation in surrounding marshes which afterwards made the lignite coal beds of the cretaceous measures that this condition of things continued for a long time and with some slight oscillations of level is evident by the different beds and quantity of the coals finally came the contraction and wrinkling of the earths crust the result of which was the rocky mountain system which as it arose from the ocean depths brought up as dry land the whole system of the plains found just west of the missouri river as well as the adjoining lands through to the pacific ocean the force that elevated the mountain range carried the granite islands up also in the movement large fissures opened in the granite miles in length and parallel with the longest axis of the island the metamorphic rocks broke at their thinnest place viz just over the granite and stand today uplifted upon each side of it those strata to the east dip towards the plains those west towards the range proper the different dips of the metamorphic rocks puzzled me for over a year as when working in clear creek county in 1880 1 I noticed it and could get at no legitimate cause although in south clear creek a short distance above the forks I 1 could see where the strata broke and at this place on the north side of the creek I 1 found primitive granite over topping with knife blade streaks of tellurium ores at that time I 1 could not understand all of its significance until a study audy of the foothills at boulder city led me to connect the two points and so solve th the e problem of the structure at clear creek this split of the metamorphic rocks turned west a couple of miles then southwest seve several ral miles the bed of south clear creek occupies the chasm charm to the mouth of chicago creek and this creek follows the rent in the metamorphic rocks almost to its source now this split and fissured granite held water like a sponge the motion of the rocks gave great heat the heated waters sought the surface through these fissures at the surface the thermal waters rapidly evaporated leaving their solids in the fissures thus were formed the veins I 1 of this tellurium belt here occurs a beautiful illustration on a stupendous scale of the theory of mineralogists that the contents of veins are derived from atoms carried in aqueous solutions from the surrounding country rocks that the contents of the vein are thereby governed by the character of the country rock here in the primitive granite do we get the veins carrying the tellurium ores and the sulphides sulp hides contained in the other veins iq in the parallel metamorphic rocks between the tellurium belt and the range we get the veins with the ordinary sulphides sulp hides but no tellurium i there are more of these tellurium belts in colorado some of them perhaps as extensive and rich as the above described veins of boulder county but nowhere so accessible ces sible and well proven the simplicity and clearness of th the e language used the intelligent and systematic presentation of proven facts aswell w ell as the absence of high sounding scientific terms give to the lines printed above such a usefulness and authority that no comments or explanations are necessary in the next issue is sue of the news the writer will present a few personal observations made during a long residence in boulder county at the ni wot mine or on the columbia aa lode 10 de to be continued |