490 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



and polished or not, depends upon whether they possess a sufficiently pretty or bizarre 

 appearance, and they ai'e sold more as curiosities than as ordinary precious or ornamental 

 stones with a definite market value. Fine examples of the kind have sold for 50s. or more, 

 but much depends upon the purchaser. 



Quartz containing Fluid Enclosures. — As already mentioned, rock-crystal 

 frequently encloses cavities which contain fluid of some kind and a bubble of gas, the 

 movement of which follows every movement of the stone. Large inclusions of this kind 

 are not common, but rock-crystal containing specially fine ones is met with in Madagsiscar, 

 in the Alps, and elsewhere. The rock-crystal of Herkimer County, New York, and of Hot 

 Springs, Arkansas, deserves special mention on this account, while the amethyst of Rabun 

 County, Georgia, is frequently cut for the purpose of displaying its large fluid enclosures. 

 Generally speaking, however, quartz which has nothing to recommend it but its fluid 

 enclosures is cut even more rarely than is hair-stone or needle-stone, and is regarded more 

 definitely as a curious natural object. 



Gold -quartz. — This is transparent or highly translucent quartz enclosing veins or 

 grains of native gold. In San Francisco and a few other large towns of western America it 

 is often cut in the form of plates for brooches, or utilised for stick -handles, cufF-links, 

 paper-weights, and other small objects of more or less utility. Some of the gold-mines of 

 California, Oregon, Idaho, and Montana have furnished very beautiful specimens. The 

 value of a stone depends upon the amount of gold it contains, which is estimated by the 

 help of the specific gravity, and also upon the beauty of the specimen. A ring-stone is worth 

 from two to upwards of ten dollars, according to its qualitv. 



Gold-quartz is now much in favour as an ornament, as is testified by the fact that in 

 some years from 40,000 to 50,000 dollars' worth of rough material suitable for cutting has 

 been sold in this region ; a single cutting works at Oakland, California, has used annually 

 10,000 dollars' worth of rough material, and a large firm of jewellers in San Francisco has 

 sold cut stones to the value of 15,000 dollars in the same period. The stones need careful 

 sorting out, and as they are very fragile and difficult to work, only about half of the material 

 destined to be cut actually reaches the market. 



White and cloudy gold-quartz is more common than the transparent variety, and 

 recently perfectly black material has been met with. White gold-quartz is artificially 

 coloured rose-red by immersing it in a solution of carmine. Attempts have been made to 

 manufacture the substance by fusing together gold and quartz in an electric furnace, not, 

 however, with very favourable results. 



The gold-quartz of Austraha, South Africa, and most of the auriferous regions, is just 

 as suitable for cutting as is the Californian, but in none of these lands is it worn to the 

 extent that it i^ in America. The auriferous quartz of La Gardette, near Bourg d'Oisans, 

 in Dauphine, 'which forms the matrix of the beautiful rock-crystals represented in 

 Plate XVII., used to be cut as an ornamental stone. About 200 pounds of gold-quartz 

 is obtained every year from mines in the neighbourhood of Mursinka in the Urals. 



Rainbow -quartz (Iris).— This is the name given to specimens of rock-crystal which 

 show brilliant iridescent or rainbow-colours over more or less large surfaces. The colour 

 has no connection with the quartz substance, but is due to purely physical causes connected 

 with the interference of light. The phenomenon is only shown by specimens of rock-crystal 

 which are penetrated by numbers of fine irregular cracks. These cracks contain films of air, 

 and to their presence is due the colours of rainbow-quartz, colours which are of exactly 

 the same nature and arise in the same way as the brilliant rainbow tints of soap-bubbles. 

 Specimens of iris are cut with a slightly convex surface, which should be as closely parallel as 



