| OCR Text |
Show 25 composed of sulfide and oxide ore with an average content of 18 to 20 per cent vanadium and surrounded by a thick envelop containing an average of about four per cent vanadium. The high-grade ore body was showing evidence of depletion by 1925, and it became necessary to mir.3 successively lower-grade material, which led to the decision to concentrate the crude ore before shipping it. In 1929 a flotation mill was built but this proved unsuccessful. In 1931, 1932 and 1933 all operations were at a standstill, owing to a combination of business depression and drastic increases in Peruvian taxes levied upon the production and exportation of vanadium. A revision of the tax laws was made in 1934 and with improved business conditions production was resumed. After the failure of the flotation mill a llxiviation process was developed, preceded by a cold-water quenching of hot roasted ore. A plant using this process had been in operation since 1934, The record shows a material though gradual decrease in the average grade of ore produced from the Mina Ragra Mine. The average vanadium concent of the ore decreased from 21.7 per cent in 1925 to 8.5 per cent in 1929 and to 4.13 per cent in 1940. A decrease of the magnitude recorded from 1925 to 19*29 meant a higher production cost and consequently a higher cost to the consumer. This placed the vanadium deposits in Colorado in a more favorable competitive position. It is |
