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UNITED STATES MINERAL RESOURCES 



the stone, is the "make," a measure of the degree to 

 which the lapidary has enhanced the physical char- 

 acteristics of a stone. Enhancement is accomplished 

 by orienting, proportioning, accurately shaping or 

 faceting, and polishing the gem to display most ef- 

 fectively its optical properties in an esthetically 

 satisfying form. 



Almost no gem stones meet the ideal definition 

 that requires beauty, durability, and rarity; and 

 some have no redeeming virtue but beauty. It is obvi- 

 ous, then, why those few stones — diamond, sapphire, 

 ruby, and emerald — that have these three qualities 

 to a high degree always have commanded a high 

 price and always have been thought of as precious 

 stones, in contrast to others considered to be only 

 semiprecious. At certain times and places opal, chry- 

 soberyl, and even pearl, turquoise, and amber also 

 have been considered precious stones, largely on the 

 basis of their rarity. Pearl and turquoise are now 

 reasonably abundant and therefore reasonably inex- 

 pensive. On the other hand, vanishingly small sup- 

 plies of stones of exceptional size and quality allow 

 ruby and Uralian alexandrite to command prices far 

 in excess of that asked for diamond of the same 

 weight. Other stones increase in price faster than 

 can be accounted for by inflation, increasing rarity, 

 or national piide. Aquamarine and tanzanite (a va- 

 riety of zoisite), for instance, have risen rapidly in 

 price recently in some parts of the world, apparently 

 very largely in response to changes in style of per- 

 sonal ornamentation — that is, in response to fad. 

 The exhaustion of ancient mining areas, the discov- 

 ery of new deposits, shifting tastes, development of 

 synthetic stones, and changes in pattern of transpor- 

 tation and marketing have combined to break down 

 these distinctions; so the tendency is for all gem 

 materials now simply to be known as precious stones. 



EXPLOITATION 



A very large fraction of all the gem materials ever 

 produced is still in existence because of the inherent 

 durability of stone, however soft, and the care nor- 

 mally lavished on costly artifacts. With the constant 

 discovery of new gem deposits, it might be expected 

 that the supply eventually would satisfy the market. 

 But the market constantly grows, along with world 

 population and affluence, and the attendant social 

 and political unrest puts an additional premium on 

 gems, for they constitute an easily portable and con- 

 centrated form of wealth. The price of any gem ma- 

 terial is not likely to drop except over the short term. 



Neither imitation nor synthetic gem stones have 

 infringed seriously on the market for natural stones, 

 nor are they likely to do so in the future,- in spite of 



the already wide variety and crystalline perfection of 

 these materials and the nearly frantic research to 

 produce others. Ruby, sapphire, spinel, rutile, emer- 

 ald, garnets, lapis lazuli, greenockite, diamond, and 

 a number of other gems have been synthesized. Some 

 of these, in both colored and colorless forms, to- 

 gether with several natural gems and other synthetic 

 materials such as strontium titanate and yttrium- 

 aluminum garnet (YAG), are marketed as inexpen- 

 sive substitutes for natural diamond. Colored glass 

 and imitation pearls, of course, fill the need for cos- 

 tume jewelry. Like Rembrandt originals, however, 

 natural gem stones will always be assured a market 

 because of the exclusiveness of rarity and genuine- 

 ness, regardless of the disparity in price between 

 them and their substitutes. 



Persistent commercial production of gem stones at 

 a profit by a private corporation is a rarity any- 

 where in the world. The rich diamond pipes of Africa 

 and the alluvial diamond deposits in Africa and in 

 Brazil are significant exceptions. The profitability of 

 government-owned mines, such as the emerald mines 

 of Colombia and West Pakistan and the diamond 

 deposits of Soviet Siberia, is not known. It is a fact, 

 however, that the privately operated Chivor emerald 

 mines in Colombia are now idle, perhaps in part 

 because a reported large fraction of production was 

 lost through pilferage and never reached the com- 

 pany's vaults. Commercial ventures to produce sap- 

 phire and ruby in Burma and in the Yogo Gulch area 

 of Montana were short lived, as was the attempt to 

 produce diamonds from the kimberlite pipes at Mur- 

 phreesboro, Ark., and the same is true at many 

 other places throughout the world. The small size 

 and diffuse nature of most deposits of gem materials 

 seem to make them amenable to exploitation only by 

 the individual miner or small group, often a family, 

 many of whom mine stones only intermittently and 

 by relatively unsophisticated methods. Yet the bulk 

 of all gem stones exclusive of diamond and emerald 

 are produced in this manner, whether they come 

 from the pegmatites of the Malagasy Republic, 

 Brazil, Maine, or California, or from the alluvial 

 deposits of Burma, Ceylon, or Idaho. 



GEOLOGIC ENVIRONMENT 



It is no tautology to say that gem stones are rare 

 because they are not plentiful. They do not form 

 "ore" deposits in the normal sense. The very precise 

 environmental conditions required to produce gem 

 stones, any gem stones, are unusual in the context of 

 the large scale and constantly changing chemical- 

 thermal-dynamic systems in which all minerals are 

 formed. Gems, when present at all, generally are 



