riEST FLOOE. 
69 
Strontianite (18b), the carbonate of strontium, is the mineral General 
from which most of the strontium nitrate is made for nse in the SiS-eralT °^ 
manufacture of fire-works, owing to the fine crimson colour 
which it gives to the flame : it is also much employed in the 
process of sugar refining. 
Cerussite (18b) is the corresponding carbonate of lead, and 
when abundant is a valuable ore of the metal. 
Calcite (18e), carbonate of calcium, is represented by an 
extraordinarily fine suite of specimens, illustrating an almost 
endless variety of crystalline form. The clear variety from 
Iceland is largely used in optical instruments for the polarisa- 
tion of light. 
Chalybite, or Spathic iron ore (20h), is the carbonate of iron 
and is a most valuable ore of the metal. The most important 
English iron ore. Clay iron-stone, is a mixture of chalybite and clay. 
Calamine (19h), carbonate of zinc, is an important zinc ore. 
Chessylite (2 Id) and Malachite (22b) are respectively the 
blue and green hydrated carbonates of copper, and are 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. 
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 the Chrysolite, while the pistachio- 
green variety is the Peridot of jewellery. 
Hiddenite (23a), a rare lately discovered emerald-green variety 
of spodumene, has been introduced as a precious stone. 
Asbestos (24c) is a variety of hornblende used in the arts ; it 
is found in long fibres, and in some of its varieties is so flexible 
that it can be woven into gloves and other articles ; examples 
will be found among the worked specimens in the Pavilion at 
the end of the gallery. The term asbestos, unquenched or un- 
quenchable, was applied to the mineral by the ancient Greeks, 
because, owing to its being unaltered by heat, wicks made of it 
were used in maintaining the sacred perpetual flres of their 
temples. JSTapkins 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 from those of 
the fuel. It is now largely employed for more prosaic purposes, 
