68 
MINERAL GALLERY. 
Silicates. such as the lining of iron safes, packing for steam-pipes and 
boilers, and in gas-stoves, for which purposes its low con- 
ductivity for heat renders it serviceable. 
Jade or Nephrite (24d), a much 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 ex- 
hibited, 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 (25 a) is another hydrated magnesium silicate : the 
ease with which it is worked and takes a good polish, its green 
colour, and varied markings render it much sought for 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, in Siberia, are remarkably 
fine ; they are 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 the 
Syrian garnet (named after Syriam in Pegu), and when cut en 
cahochon, 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 i 
higher specific gravity. Among the specimens of Epidote (27c) 
a remarkable suite from the Untersulzbachthal is exhibited. 
Mica (28a) is the name given to a group of minerals differing j 
much from each other in chemical composition and optical pro-j 
perties, but having as a common character an easy cleavage in a 
single direction, and thus affording plates remarkably thin, 
