88 
MINERAL GALLERY. 
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 Riband-Jasper. 
The Lydian or Touch-stone (15a), by reason of its hardness 
