| OCR Text |
Show 32 the vanadium is an inherent part of the sandstone in which It occurs and is sedimentary in origin,. The vanadium occurs near the base of the Entrada sandstone of Jurassic age, This sandstone is exposed in cliffs along the steep valley slopes of the San Miguel River and its tributaries, cliffs that are easily recognized by their massive character and light-buff to pink,colors. The vanadium near Placerville occurs as a black, micaceous mineral, roscoelite, that fills the spaces between sand grains, and the ore is known as roscoelite ore. The vanadium ore is dark-gray to black, depending on the amount Of roscoelite present; the intensity of the color is a relative measure of the vanadium content. A little carno-tite, also a vanadium-bearing mineral and formerly Important as a source of radium in the carnotite area to the west, occurs locally along Joints but is not important as an ore mineral in the Placerville area. The average vanadium content of the ore mined was 1,5 to 2 per cent. Thin beds of sandstone containing vanadium are extensive and commercial thicknesses, roughly two feet or more, have been found to be continuous for several hundred feet along the bedding of the sandstone, The first recorded^ production of vanadium was in Hutchinson, W. S., Boericke, H., and Hess F. L. Vanadium in international control of minerals, p. 160, Min. Met. hoc. America and Am. Inst. Min. Met. Eng., iy^ |
