Chaffee County Colorado Gold Production
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The Monarch district is centered around the town of Garfield about 17 miles west of Salida. The district has produced chiefly silver, lead, and zinc, some copper, and a small amount of byproduct gold.
The first ore was discovered in the Monarch district in 1878. Other discoveries followed shortly, and by 1882 most of the large ore deposits in the region had been found. Transportation difficulties inhibited early development, but by 1883 a railroad was built to Monarch which permitted cheap and rapid transportation to the smelter at Pueblo. Oxidized ore rich in silver and lead was mined during the next 10 years, and production was large. In 1893, when the price of silver dropped, most mines were closed, and the district was nearly deserted (Crawford, 1913, p. 195-196). A demand for zinc revived the district, and in 1906 shipments of zinc carbonate ore began and continued for many years (Henderson, 1926, p. 43), especially during World War I. Between 1924 and 1940 activity was only intermittent. During World War II a few mines reopened, but these were closed again shortly after the war.
The Madonna mine, which is credited with almost 50 percent of the total output of the district, pro¬duced 4,652 ounces of gold between 1883 and 1911 (Crawford, 1913, p. 239). Total gold production of the district through 1959 was probably from 15,000 to 20,000 ounces.
The bedrock of the district is of three ages— metamorphic and igneous rocks of Precambrian age, sedimentary rocks of Paleozoic age, and intrusive rocks of Tertiary age. The Precambrian rocks are schists and gneisses and intrusive masses of Pikes Peak and Silver Plume (?) Granites. The Paleozoic rocks, which contain productive ore horizons, are about 6,000 feet thick and range in age from Cambrian to Permian (?). The sedimentary rocks have been eroded from a large part of the area, but patches have been preserved in synclines and in down-faulted blocks. The intrusive rocks of Tertiary age, the largest of which is the Mount Princeton batholith, are chiefly of quartz diorite and quartz monzonite composition (Dings and Robinson, 1957, p. 5-27).
The ore deposits in the Monarch district are replacement bodies, chiefly in the Paleozoic limestone and dolomite beds, and fissure veins. The Manitou Dolomite of Ordovician age and beds in the upper part of the Leadville Limestone of Mississippian age are especially favorable host rocks. The largest and richest replacement deposits are along faults in these beds near or adjacent to the Mount Princeton batholith. The chief sulfide minerals are galena, pyrite, sphalerite, some chalcopyrite, and local pyr-rhotite. Much of the pyrite is gold bearing, and practically all the galena carries some silver, in places large amounts. The gangue consists of quartz and recrystallized limestone or dolomite. The bulk of all ore mined was at least partially oxidized, and the ore in the replacement deposits was more thoroughly and deeply oxidized than the ore in veins. Oxidation in the replacement deposits extends to a depth of 1,000 feet or more, whereas the oxidized ore in the veins is only a few feet deep.
Most of the veins in the Monarch district occur in the Mount Princeton Quartz Monzonite and in the sedimentary rocks of Pennsylvanian age; a few are found in some of the older sedimentary rocks and in the Precambrian rocks. The mineral assemblage in the veins is very similar to that of the replacement bodies. The unoxidized parts of the veins consist chiefly of galena, sphalerite, and pyrite, and some chalcopyrite in a gangue of white quartz. Silver is present in most of the ores, but gold is erratically distributed (Dings and Robinson, 1957, p. 81-85).