riEST FLOOR. 
51 
Blende (4b) is a valuable zinc ore, and contains 67 per cent, 
of zinc and 33 per cent, of sulphur. 
Galena (4e) is by far the most important ore of lead (lead 87, 
sulphur 13). 
Copper-glance (3e) is an important ore of copper (copper 80, 
sulphur 20). 
Cinnabar (3h) is the ore from which mercury or quicksilver 
is obtained (mercury 87, sulphur 13). 
Pyrites (5d), one of the most common of minerals, is a com- 
pound of iron and sulphur (iron 47, sulphur 53). 
Erubescite (5e), Copper pyrites (5f), and Tetrahedrite, or Grey 
Copper ore (7a), are all valuable copper ores. 
Common salt is represented in case 8f, and Fluor, a com- 
pound belonging to the same division, begins at case 7e. 
The next division, consisting of compounds of oxygen and 
including most of the stony minerals, begins with Cuprite (10a), 
an important ore of copper (copper 89, oxygen 11). 
Spinel (lOe), in its transparent varieties, is one of the pre- 
cious stones : the deep red is the Spinel Euby (less dense and 
less hard than the true ruby), the rose-tinted is the Balas Euby, 
and the yellow or orange-red is the Eubicelle of the jewellers : 
sometimes, too, it has a dark blue colour. On account of their 
hardness the less valuable specimens are used for the jewelling 
of watches. - 
Magnetite, or Magnetic iron ore (lOf ), is the richest and most 
valuable of the ores of iron, of which metal it contains 72 per 
cent. It is the natural loadstone. 
Chrysoberyl (9e) is another of the precious stones. The beauti- 
ful greenish-yellow variety, almost equal in lustre and hard- 
i ness to the sapphire, is the Oriental Chrysolite of the jewellers ; 
another variety, with a peculiar play of light, is the true Cat's- 
eye; while a third, green by sunlight but red by candle- or 
lamp-light, is the stone known as Alexandrite. 
Corundum (9h), when clear and of the proper colour, is, after 
the diamond, the most precious of stones. When pure it is the 
I colourless variety known to jewellers as the Lux-sapphire : but 
jwith very minute traces of colouring ingredient it assumes the 
irichest and most varied hues ; when red it is the true Euby; when 
I azure it is the Sapphire ; while the yellow, green, and purple 
