438 



UNITED STATES MINERAL RESOURCES 



EXPLOITATION PROBLEMS 



Exploitation problems in nickel mining and proc- 

 essing are in part the same as or similar to those 

 for copper. Air pollution is a major problem around 

 the smelters, and it is likely that strict controls on 

 smoke exhalations will soon be enforced throughout 

 the United States. Most other countries are less con- 

 cerned with air pollution at the present time, but 

 demands for stricter control are also increasing in 

 those countries. 



Another major consideration, particularly appli- 

 cable to some areas of large potential laterite de- 

 velopment, is that the political climate of some 

 countries is not conducive to huge long-term invest- 

 ment (hundreds of millions of dollars) and a long 

 development period (5 years or more for a large 

 operation) . 



The cost and difficulty of recovering nickel-bearing 

 nodules from mid-ocean depths of 3,500-4,500 

 meters are major problems. Furthermore, suitable 

 refining methods have yet to be demonstrated. The 

 availability of large and relatively low-cost sources 

 of the component metals on land also reduces in- 

 centive to their development. 



GEOLOGIC ENVIRONMENT 



GEOCHEMISTRY 



Nickel is widespread in nature and is estimated 

 to be the fifth most abundant element of the earth. 

 Estimates of the nickel content of the earth's crust 

 range from 0.008 to 0.02 weight percent (Fleischer, 

 1953). Ultramafic igneous rocks — dunite, peridotite, 

 and pyroxenite — contain the most nickel, 0.1-0.3 

 percent; Vinogradov (1956) estimated the average 

 nickel content of these rocks to be 0.12 percent. His 

 estimates for other rock types are: mafic igneous 

 rocks (basalt, gabbro, norite, and related rocks), 

 0.016 percent; neutral igneous rocks (diorite and 

 andesite), 0.0055 percent; silicic igneous rocks 

 (granite, rhyolite, and related rocks), 0.0008 per- 

 cent; and sedimentary rocks (clay and shale), 

 0.0095 percent. 



A generally accepted theory is that the core of 

 the earth, 4,300 miles in diameter, has a composi- 

 tion similar to that of iron meteorites, most of which 

 are kamacite — native iron with a nickel content of 

 almost 7 percent. Inasmuch as the margin of the core 

 is 1,800 miles below the earth's surface, this vast 

 amount of nickel will probably never become avail- 

 able to man. The crust of the earth (about 10 miles 

 thick), from which man must obtain the nickel he 

 needs, contains only 0.003 percent of the total nickel 

 in the earth, as computed from data given by Mason 

 (1958, p. 44, 50). 



The mantle, lying between the crust and the core 

 of the earth, is nearly 1,800 miles thick and is be- 

 lieved to be peridotitic. Rocks of this ultramafic 

 zone, like similar rocks exposed at the surface, may 

 contain 0.1-0.3 percent nickel. Because the mantle 

 makes up more than two-thirds of the total mass 

 of the earth, it probably contains a large quantity 

 of nickel. 



The peridotite and related mafic rocks that have 

 intruded the crust of the earth, and are in part 

 exposed at the surface, probably have been derived 

 largely from the mantle. Furthermore, most of the 

 known nickel ore deposits are closely associated 

 with mafic and ultramafic intrusive rocks, and the 

 nickel in the ore bodies was probably derived either 

 from the intrusives themselves or from similar rocks 

 at depth. Thus the original source of most of the 

 nickel ore bodies found in North America and else- 

 where in the world was probably the mantle. 



NICKEL MINERALS 



The nickel minerals are given in table 86. The 

 nickel-iron sulfide pentlandite [(Fe,Ni)9S8] is the 

 principal present economic source of nickel, and 

 garnierite (nickel-magnesium hydrosilicate) is next 

 in economic importance. Garnierite — also called 

 nickel gymnite, genthite, noumeite, and nepouite — 



Table 86. — Nickel minerals 



Mineral Formula 



Native nickel-iron NiaFe 



Pentlandite (Fe,Ni)9S6 



Bravoite (Fe,Ni)S2 



Violarite NizFeSi 



Vaesite NiS^ 



Polydymite NisS, 



Millerite NiS 



Heazlewoodite Ni.iS2 



Siegenite (Ni,Co)3S. 



Linnaeite (Co.Fe.NDaS, 



GersdorfRte NiAsS 



Niccolite NiAs 



Rammelsbergite NiAss 



Chloanthite (Ni,Co) Asa-i 



Smaltite (Co,Ni)As3-x 



Skutterudite (Co,Ni)As3 



Maucherite NinAse 



Breithauptite NiSb 



Ullmannite NiSbS 



Parkerite NisBi^Ss 



Annabergite NiaCAsOO^-SH^O 



Morenosite NiSOi-7H.O 



Zaratite NiCo3-2Ni(0H)2 



•4H2O 



Garnierite Nickel-magne- 

 sium hydrosili- 

 cate 



Rare. 

 Common. 

 Minor; 

 second- 

 ary. 

 Do. 

 Rare. 



Do. 

 Minor ; 

 second- 

 ary. 

 Rare. 

 Minor. 

 Do. 

 Do. 

 Do. 

 Rare. 

 Do. 

 Do. 

 Do. 

 Do, 

 Do. 

 Do. 

 Do. 

 Rare; 

 second- 

 ary. 

 Do. 

 Do. 



Common ; 

 second- 

 ary. 



