SILICATES. 
91 
safes, packing for steam-pipes and boilers, and in gas-stoves, 
for which purposes its low conductivity for heat renders it 
serviceable. 
Jade or Nephrite (24d), a valued mineral, belongs to the 
same mineral group as Hornblende. The various shades of 
colour and the beautiful polish which this tough mineral will 
take are illustrated by specimens in the case. The worked 
specimens from New Zealand, of which there are several 
exhibited, are now rare. An immense water-worn mass, 
found some years ago in Asiatic Eussia, is shown in the 
pavilion. 
Meerschaum (23g), the light soft porous mineral used for 
tobacco-pipes, is a hydrated silicate of magnesium. Ser- 
pentine (25a) is another hydrated magnesium-silicate : the 
ease with which it is worked and polished, its green colour and 
varied markings render it much sought after as a material 
for fire-places, tables, and other indoor work : exposed to the 
weather it soon loses its polish. 
Topaz (25d) in its clear varieties is one of the precious 
stones. The crystals from the Urulga river, Siberia, are 
remarkably fine, and of a delicate brown colour, but are 
kept covered, as the action of light speedily bleaches them. 
The yellow crystals from Brazil assume a peculiar pink colour 
when heated, and are then known to jewellers as Burnt or 
Pink Topaz. 
Garnet also belongs to the group of precious stones ; wdien 
the red is tinged with violet, the stone is the Almandine or 
Syrian garnet (named after Syriam in Pegu), and when cut en 
mhochon, the Carbuncle of jewellery (26f); the Cinnamon- 
stone or Hessonite is yellow (26e) ; the Pyrope and the 
Bohemian garnet are blood-red (26e) ; Uvarovite is a green 
chrome-garnet (26h). 
Jadeite (27a) is one of the green stones which, under the 
name of Jade, are wrought into ornaments in China : from 
jade it is distinguished by its chemical composition, structure, 
and higher specific gravity. Among the specimens of Epidote 
(27c) a remarkable series from the Untersulzbachthal is ex- 
hibited. 
Mica (28a) is the name given to a group of minerals differing 
