52 NATURAL HISTORY. [NORTH 
described by Mr. Smithson), from Siberia, &c., probably produced 
by the decomposition of galena;—with this is placed the beudantite , 
a mineral from Horhausen on the Rhine, which, according to Wol¬ 
laston, consists only of the oxides of lead and iron.— Oxide of tin or 
tin-stone , divided by Werner into common tin-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. 
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, being one of the matrices of the common 
corundum of the Carnatic. — The diaspore from the Ural, and the 
gibbsite from Massachusetts, are hydrates of alumina. 
Aluminate of magnesia —the spinel: 0 among its principal varieties 
may be specified the blue spinel of Aker in Slidermannia, and the 
brown, often in crystals of considerable dimension, from New r Jersey; 
—the ceylonite or pleonaste, and the automolite (also called gahnite ), 
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 zinc; —the chrysoberyl or cymophane , considered as an alu¬ 
minate of glucine and of iron, among the specimens of which may be 
specified the large crystals from the Ural and from Brazil, those in a 
matrix of quartz and feldspar with garnets, from Haddam in Connec¬ 
ticut, and also those from Saratoga and New York;—the mineral called 
gum-lead ( plomb gomme), 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. 
Case 20. Amethyst quartz of various tints, in grouped crystals, &c. 
.—Rock crystal: various modifications of crystalline forms: small 
dodecahedral and other crystals, known by the names of Gibraltar 
diamonds, Bristol diamonds, &c. ; varieties of colour, according to 
which this substance obtains the familiar denominations of smoky topaz 
