88 MiNEftAL GALLEftV. , 



the richest and most varied hues ; when red it is Ruby, 

 when azure Sapphire, while the yellow, green, and purple 

 varieties are known respectively to jewellers as the Oriental 

 Topaz, Emerald,^ and Amethyst. Although at first used to 

 suggest that the stones, instead of being ordinary topaz, 

 emerald, and amethyst, but others of similar colour coming 

 from the East (India, Ceylon, Siam, Pegu, &c.), the prefix 

 " oriental " was afterwards understood to refer only to the excel- 

 lence of their characters. The Star-stone, another variety of 

 Corundum, when placed in a strong light shows a six-rayed star. 

 Haematite (11a) is a valuable ore of iron. 

 Cassiterite, or Tin-stone (llf), is the ore of tin, of which metal 

 it contains 79 per cent. 



Zircon (13b), when clear and without flaws, is one of the 

 precious stones : one variety with peculiar red tints being the 

 Hyacinth or Jacynth, while the colourless, yellowish, and dull 

 green phases are termed Jargoon : the colourless variety, owing to 

 its high refractive power, approaches the Diamond in brilliancy. 

 Quartz, which is silica, the oxide of silicon, is the most 

 common of minerals. In its clear and transparent variety 

 it is the Crystal of the ancients and the Eock-Crystal of 

 modern times ; while it is the Brazilian Pebble of spectacle- 

 makers (14b). After the clear come the smoky varieties, in- 

 cluding the Scotch Cairngorm and Occidental Topaz (14g). 

 Next follows the Amethyst (14h), one of the less valuable, though 

 one of the most beautiful of ornamental stones. The Quartz 

 Cat's-eye (13f) is a variety presenting the opalescence, although 

 not the hardness or brilliancy, of the true Cat's-eye already 

 referred to : the opalescence being due to enclosed fibres of an 

 asbestos-like mineral in the specimens from Ceylon, and to 

 fibres of Crocidolite in the blue, and of altered Crocidolite in the 

 brownish-yellow specimens from South Africa. 



Jasper (13g) is a coloured mixture of silica and clay, dis- 

 tinguished from ordinary quartz by its opacity and dull earthy 

 fracture. It is of various colours, chiefly red, brown, yellow, 

 and green; and the colours are arranged sometimes in a 

 nodular form as in Egyptian Jasper, at other times in stripes 

 as in Eiband-Jasper. 



The Lydian or Touch-stone (15a), by reason of its hardness 



