gallery.] natural history. (Minerals.) 63 
or tin-stone , divided by Werner into common iin-stone and wood-tin: 
among the specimens of the former (chiefly from Cornwall, Saxony, 
and Bohemia) may be specified the greyish-white crystals resembling 
scheel-ore or tungstate of lime, the regular and macled crystals, the 
pebble-like and granular tin-stone (shoad-tin, stream-tin, grain-tin, &c.), 
the columbiferous oxide of tin from Finbo in Sweden; among the 
varieties of wood-tin, are some composed of radiated-fibrous small 
globules, others marked with concentrically disposed, brown and yellow 
colours, and called toad’s eye wood-tin, fortification wood-tin, &c. To 
which are added some specimens of metallic tin, the result of smelting, 
of which the more remarkable, on account of its locality, is that cast 
in the form of thick wires, brought by Capt. Clapperton from Soudan 
in Africa. 
In the next Case begin the oxides of electro-negative bodies, and 
their various combinations. 
Case 19. Alumina and Aluminates. To the former belongs the 
corundite , divided into noble and common corundite, the former com¬ 
prehending the precious stones commonly called oriental gems (the 
sapphire, ruby, oriental amethyst, oriental topaz, oriental emerald), of 
the crystallized forms of which the principal modifications are here 
deposited; the latter, to which the name of corundum is more espe¬ 
cially applied, affords one of the hardest and best polishing materials 
to the lapidary: from Bengal, Mysore, China, the Carnatic (Werner’s 
diamond spar), Lapland, Piedmont, &c. As appendix to these are 
added, the emery , a substance which derives its hardness and consequent 
usefulness for polishing to an admixture of blue or grey corundum ; 
and the indianite of Bournon, which sometimes occurs as matrix of the 
common corundum of the Carnatic. 
As hydrates of alumina are to be particularized, the diaspore from the 
Ural, and the gibbsite from Massachusetts, together with the hydrargillite 
of Rose (not of Davy), from Lissensko, in the Shisshimskian moun¬ 
tains. 
Aluminate of magnesia —the spinel: 0 among its principal varieties 
may be specified the blue spinel of Aker in Siidermannia, and the 
brown, often in crystals of considerable dimension, from New Jersey; 
—the ceylonite or pleonaste, and the automolite (also called gahnite) 9 
from Fahlun in Sweden and from Franklin in New Jersey, are, the 
former an aluminate of protoxide of iron and magnesia, the latter an 
aluminate of zincthe chrysoberyl or cymophane , considered as an alu¬ 
minate of glucine and of iron, among the specimens of which deserve 
particular mention the large crystals from Brazil and from the Ural, 
(the latter green variety, but of a columbine red by transmitted light, 
has been called alexandrite ), those in a matrix of quartz and feldspar 
with garnets, from Haddam in Connecticut, and also those from Sa¬ 
ratoga and New York;—the mineral called gum-lead (plomb gomme) 9 
which occurs at Huelgoet in Brittany only, and is a hydrous aluminate 
of lead. 
The five following Cases contain the acid or oxide of silicium (silica), 
the numerous varieties of which, formerly considered as so many 
distinct species, are mostly indebted for their generally very striking 
external characters to the admixture of matter foreign to the species, 
or to other casual circumstances that prevailed at their formation. 
