478 SYSTEMATIC DESCRIPTION OE PRECIOUS STONES 



The material is obtained in the neighbourhood from a conglomerate of Tertiary age, in 

 which it occurs in the form of pebbles. A once famous centre of this industry is Delhi, the 

 bowls, vases, drinking-cups, and other objects carved there being renowned for beauty of 

 design and skill in workmanship. The art is now forgotten, but the old mines at Aurangpur, 

 fifteen miles south of Delhi, whence rough material was obtained, are still to be seen. 

 There are many other localities for rock-crystal in India, but none appear to have any 

 industrial importance. 



Rock-crystal is \ury abundant in America, and specially so in Brazil. Not only are 

 large amounts of very fine and clear rock-crystal obtained in this country, but also many of 

 the coloured varieties of quartz (amethyst, citrine, &c.). The rock-crystal is much used for 

 spectacle-lenses and other optical instruments, and for various other purposes. Brazilian 

 rock-crystal (" Brazilian pebble ■") is easy to obtain, and is very cheap, and has therefore 

 ousted other material from the market. A finished spectacle-lens cut in Brazil from 

 Brazilian material, according to Mr. G. F. Kunz, of New York, fetches less than the cost 

 of cutting a lens in that city. The States in which the mineral is most abundant are Minas 

 Geraes, Sao Paulo, and Goyaz, especially in the last named in the Serra dos Cristaes, sixty-five 

 miles from Santa Lucia and 200 miles from the town of Goyaz. The crystals hei-e lie about 

 loose on the ground, and some weighing sixty-four pounds have been found in the surface 

 soil. Beside the rock-crystal there is quartz of every colour and quality. Eor a long time 

 the occurrence gave employment to 200 persons, who in the space of two years collected 

 7000 tons of material. Later, however, the demand fell off^', and finally almost ceased, 

 mining operations becoming at the same time less active. 



There are also many localities for rock-crystal in the United. States of North America. 

 At Chestnut Hill, in the State of North Carolina, are found pure crystals weighing a 

 hundredweight or more ; the largest American crystal known was met with there and 

 weighed 131 kilograms (288 pounds). The next largest American crystal weighing 86 

 kilograms came from Alaska. On Lake George, in New York, and over a wide area in 

 Herkimei' County, in the same State, rock-crystals of small size but developed on all sides 

 occur in cavities in the Calciferous sandstone. In lustre, transparency, and purity these 

 crystals rival even those of Carrara, in Italy. They have been collected in large numbers 

 for upwards of half a century, and both cut and rough stones are sold in the neighbourhood, 

 mostly to tourists, under the name "Lake George diamonds" or some similar term. Some 

 specimens enclose large drops of water and others black grains, often of considerable 

 size, of a bituminous substance ; in the former case the stones are of greater, and in the 

 latter of less, value than ordinary specimens. Water-clear rock-crystal occurs in abundance 

 in Crystal Mountain and elsewhere within a forty miles radius from Hot Springs, in 

 Arkansas. Waggon-loads of these so-called " Arkansas diamonds," which are found in 

 cre\'ices in red sandstone, are brought by the farmers to Hot Springs and Little Rock, 

 where thousands of dollars' worth are sold to the visitors at the baths. In the Washita 

 river at Hot Springs there are quartz pebbles like those found in the Rhine, and so eagerly 

 are these sought for by tourists that the supply has ])een artificially increased by grinding 

 _^i^ether fragments of rock-ciystal in rotating barrels. Rock-crystal occurs abundantly also 

 in Canada. 



Rock-crystal of fine quality has recently been found at Mokelumne Hill, Calaveias 

 County, California ; an account of this occurrence has been given by Mr. G. F. Kunz in his 

 report on precious stones for 1898. The large crystals are found embedded in the gravels 

 and sands of an ancient ri\er channel ; they are only slightly A\ater-\vorn, but are usually 

 much stained on the exterior. One crystal measures 19 by 15 by 14 inches, and another 



