COBALT 



145 



pounds of cobalt for the national stockpile of stra- 

 tegic minerals, from 1954 to 1961 (Cornwall and 

 Vhay, 1967,p. 70). 



About 400,000-600,000 pounds of cobalt is pro- 

 duced annually from pyrite as a byproduct of mining 

 magnetite at Cornwall, Pa. (Andrews, 1962, p. 161). 

 The mineral production from Cornwall and the 

 Grace mine, near Morgantown, Pa., is now virtually 

 the only primary source of domestic cobalt. 



Small amounts of cobalt were produced from the 

 veins of the Blackbird district, Idaho, during World 

 War I, and about 14 million pounds was produced 

 from 1951 to 1959, when the mines closed. The mines 

 were still inactive in 1972. According to Andrews 

 (1962, p. 162), the Magnesia Talc Co., at Burlington, 

 Vt., has produced concentrates containing cobalt and 

 nickel as a product in the froth flotation of talc. Not 

 much information is available, but the concentrates 

 are believed to contain 0.015 percent cobalt and 0.2 

 percent nickel. 



Small production of cobalt has been reported from 

 other places in earlier times — near Chatham, Conn., 

 the Goodsprings and Table Mountain districts, Ne- 

 vada, and the Quartzburg district, Oregon. 



The production of cobalt from laterite ores has 

 been small during the past few decades, but these 

 deposits, which can be mined at relatively low cost 

 by open-pit methods, are destined to become increas- 

 ingly important. The cobaltiferous laterite, or asbo- 

 lane, deposits of New Caledonia intermittently have 

 been the leading world producers of cobalt. Although 

 production from this source has been insignificant 

 since 1911, the total cobalt reserves are estimated to 

 be large and readily available for renewed produc- 

 tion. In more recent years, chiefly since the begin- 

 ning of World War II, cobalt has been recovered 

 from laterite ores in Cuba. It is believed that with 

 proper economic incentives this production can be 

 increased substantially. Similar large deposits occur 

 in the Phihppines, Indonesia, the U.S.S.R., Western 

 United States, Guatemala, and many other countries. 



The history of cobalt production clearly indicates 

 that large ore deposits containing some small 

 amounts of cobalt are widespread in the world, but 

 virtually none are workable for cobalt content alone. 

 The current utilization of the world's cobalt is pri- 

 marily a matter of economics and technology, and 

 not a question of geologic availability. 



Mining, smelting, and other environmental con- 

 siderations in the production of cobalt are identical 

 with those considered in the chapters of this volume 

 dealing with iron, copper, and nickel. 



GEOLOGIC ENVIRONMENT 



GEOCHEMISTRY 



Cobalt (atomic number, 27; atomic weight, 58.93) 

 is a metallic element whose abundance in the earth's 

 crust is estimated to be about 20 ppm (parts per 

 million). It is a simple element consisting in terres- 

 trial materials almost exclusively of the single stable 

 nuclide Co'" except for minor traces of fission-pro- 

 duced and cosmic-ray-produced Co*° (Rankama, 

 1963, p. 393-394) . In addition, nine radioisotopes of 

 mass numbers 54-58 inclusive, and 60, 61, 62, and 

 64, have been made artificially, of which Co'" is a 

 highly important source of radioactivity (Rankama, 

 1963, p. 393). The ionic radius of cobalt in sixfold 

 coordination is 0.72A for Co=+ and 0.63A for Co^+, 

 closely similar to the ionic radii of Mg^+, Mn^+, 

 Fe-+, Fe'+, Ni^+, and possibly Zn=+, with all of 

 which it is commonly associated in nature. 



The principal concentrations of cobalt are found 

 in mafic and ultramafic igneous rocks. As shown in 

 table 30, the cobalt content progressively decreases 



Table 30. — Average cobalt content of igneous rocks 



[Compaed by J. S. Vhay] 



Rock type 

 (listed in order of Co Ni Ni/Co 



increasing differentiation) (ppm) (ppm) 



Ultramafic rocks 270 1,900 7 



Gabbro 51 133 2.6 



Basalt 41 102 2.5 



Diabase 31 65 2.3 



Intermediate i^eous rocks — 14 27 1.9 



Felsic rocks 5 5.7 1.1 



in a differentiation series from ultramafic to acidic 

 rocks. The ratio of nickel to cobalt also decreases 

 during differentiation, chiefly because cobalt enters 

 the lattice of early crystallizing magnesium silicates 

 less readily than nickel, which has an ionic radius 

 closer to magnesium. 



The concentrations of cobalt in sedimentary rocks 

 are not well known, in part because of the past diffi- 

 culty in analysis for the small amounts present in 

 most types of rock. Average figures from a variety 

 of sources indicate about 4 ppm Co in sandstone, 

 6 ppm in carbonate rocks, and about 40 ppm for 

 shale, clay, mudstone, and siltstone. Few analyses of 

 cobalt in iron-rich sedimentary rocks are available; 

 however, Krauskopf (1955) indicated a range of 

 20-300 ppm. The cobalt content of phosphorite is 

 reported between 2 and 50 ppm (Krauskopf, 1955). 

 Somewhat higher concentrations are reported in 

 sedimentary deposits that are rich in organic car- 

 bon. As much as 500 ppm cobalt has been reported 

 in ashed carbonaceous shale, 148 ppm in ashed coal. 



