90 
MINER A.L GALLERY. 
Carbonates. Witherite, the carbonate of barium (18a), is used in the 
manufacture of plate-glass and in France in that of beet-sugar. 
Strontianite (18b), the carbonate of strontium, is one of two 
minerals from which strontip-m -nitrate is made for use in the 
manufacture of fireworks, owing to the fine crimson colour 
which the salt gives to the flame : the strontium minerals are 
also employed in connection with sugar-refining. Cerussite (18b) 
is the corresponding carbonate of lead, and when abundant is 
a valuable ore of that metal. 
Calcite (18e), a carbonate of the metal calcium, is represented 
by a fine suite of specimens, illustrating an almost endless 
variety of crystalline form. The clear variety from Iceland is 
largely used in optical instruments for polarising light. 
Chalybite, or Spathic iron ore (20h), is the carbonate of 
iron, and a valuable ore of that metal. The most important 
English iron-ore, Clay Iron-stone, is a mixture of chalybite and 
clay. Calamine (19h), a carbonate of zinc, is an important zinc- 
ore. Chessylite (21d) and Malachite (22b) are respectively the 
blue and green carbonates of copper, and are used as ores of 
that metal. Malachite is found in large masses ; and by reason 
of the high polish which it takes and its beautiful markings, is 
much used for ornamental work of various kinds. 
Silicates. Passing to the Silicates, we come to Olivine (22f), one of the 
less hard and least valued of the precious stones ; when of a 
yellow colour it is known as Chrysolite, while the pistachio- 
green variety is the Peridot of jewellers. Hiddenite (23a), a 
rare emerald-green variety of Spodumene, is from Stony Point, 
North Carolina. 
Asbestos (24c), a variety of Hornblende (a black mineral 
common in rocks of igneous origin) used in manufactures, is found 
in long fibres, and in some of its varieties is so flexible that it 
can be woven into gloves and other articles. The term asbestos, 
meaning unquenched or unquenchable, was applied by the ancient 
Greeks, because, owing to being unaltered by heat, wicks 
made of the mineral were used in maintaining the perpetual 
sacred fires of their temples. Napkins of asbestos were cleaned 
by being thrown into the fire ; asbestos- cloth was also used in 
the process of cremation to keep the ashes of the body distinct 
i'voui those of the fuel. It is now employed for lining iron- 
