Possible substitute materials. Substitutes are available for many of the applications of the rare-earth 

 elements. Rare-earth oxides, arsenic, and selenium are partly interchangeable for decolorizing glass but 

 rare-earth compounds have no substitutes in the production of special glasses for absorption of the 

 ultraviolet or yellow portions of the light spectrum. In carbon-arc electrodes, rare-earth compounds are 

 far superior to any otlier material. 



Potential from tnarine sources. The rare earths include 15 chemically similar elements. They are 

 concentrated in monazite (discussed under thorium), xenotime, allanite, apatite, and bastnaesite. 

 Xenotime occurs commonly with monazite but is much less abundant. Allanite is not a hard chemically 

 resistant mineral so it rarely finds its way into placer-type deposits from parent granitic and 

 metamorphic rocks in which it is sparsely distributed. 



Apatite, the principal phosphate-bearing mineral in phosphorite nodules, may contain significant 

 quantities of rare earth elements. However the rare earth concentrations in apatite are not sufficient to 

 brighten the future of the offshore mining of phosphatic nodules. 



A major source of rare earths is a deposit containing bastnaesite in southeastern California where 

 reserves are reported to contain four to five million tons. At the 1966 rate of U.S. demand (5,700 tons) 

 this supply would suffice for 600 to 800 years. If demand for rare earths were to increase suddenly or 

 recovery technology to advance, on shore phosphate mines might become an important source. 



Procurement of rare earths from the sea floor seems limited at present to monazite recovery, which is 

 tied closely with black sand mining. 



SALT 



Uses. The largest users of salt in the United States are the chemical industries, which consume about 

 65 per cent. The manufacturers of chlorine and its coproduct sodium hydroxide consume about 39 per 

 cent of national production; manufacturers of soda ash consume about 21 per cent; all other chemical 

 users consume 4 to 5 per cent. Salt is also used in fairly large and growing amounts on roads to melt ice 

 and snow, in water softeners, and in the growing and processing of food. Table salt accounts for about 

 3 per cent of salt usage. 



Present levels of utilization of salt in million short tons. 



World (1966 production) 

 United States (1966 demand) 



Ranges of demand projection to the year 2000. 



122.5 

 36.5 



Prospective supplies and prices. Supplies of salt in the form of natural and artificial brines and rock 

 salt are more than adequate to meet present and future domestic demands at low cost. The rest of the 

 world has numerous salt deposits that are minable at costs comparable to those in the United States if 



VlI-151 



