SILICATES; 91 



safes, packiilg for steam-pipes and boilers, and in gas-stoves, 

 for whicli 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 mtaeral wiU 

 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 Uridga 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 ; when 

 the red is tinged with violet, the stone is the Almandine or 

 Syrian garnet (named after Syriam in Pegu), and when cut en 

 cabochon, 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 



