50 
NATURAL HISTORY. (Minerals.) 
[north 
cohalt-ochre, which seem to be hydrates of the oxides of cobalt and 
manganese, frequently mixed with oxide of iron_ Oxide of uranium, 
or uran-ochre, occurring at Johanngeorgenstadt and Joachimsthal; 
together with what is called pitch-ore, considered, when in its pure 
state, as a hydrous protoxide of the same metal; which, however, 
requires further confirmation. 
Case 18. Oxide of lead: —the native minium from Hessia (first 
described by Mr. Smithson), from Siberia, &c., probably produced 
by the decomposition of galena.— Oxide of tin or tin-stone\cassiterite, 
Beud.), 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 mackled crystals, the 
pebble-like and granular tin-stone (shoad-tin, stream-tin, grain-tin, &c.); 
—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., also in supposititious crj^stals after feldspar, at St. Agnes, 
Cornwall. (To w’hich are added some specimens of metallic tin, the 
result of smelting of w'hich the more remarkable, on account of its 
locality, is that cast in the form of thick wires, brought by Capt. Clap- 
perton from Soudan in Africa, and mentioned in the Appendix to his 
Journal.) 
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 
corundum or corundite, divided into nohle and common corundite, the 
former comprehending the precious stones commonly called oriental 
gems (the sapphire, ruby, oriental amethyst, oriental topaz, oriental 
emerald), of the crystallized forms of which the principal modifi¬ 
cations are here deposited;—Jhe latter, to which the name of corundum 
is more especially applied, aflbrds one of the hardest and best polishing 
materials to the lapidary: from Bengal, Mysore, China, the Carnatic 
(Werner’s diamond spar), New Jersey, Lapland, Piedmont, &c. As 
appendix to these are added, the emery, a compound substance which 
derives its hardness and consequent usefulness for polishing to blue 
or grey corundum ; and the indianite of Bournon, which sometimes oc¬ 
curs as matrix of the common corundum of the Carnatic. As hydrates 
of alumina are to be particularized, the diaspore from the Ural, and 
the hydrargillite of G. Rose : the latter a mineral from Shimshimskaja 
Gora, which is to be considered as crystallized gihhsite, if Torrey’s 
analysis of the latter be correct; but as, according to Hermann, the 
gibbsite contains upwards of S7 p. c. of phosphoric acid, it is at present 
placed with the phosphates (Tab. 57) : the mineral called wavellite of 
A^iUaricca, being no phosphate, is now referred to the hydrargillite, with 
which it agrees in its chemical composition. 
The aluminates of magnesia: —the spinel, among the principal va¬ 
rieties of which, besides the red and violet, may be specified the' blue 
spinel of Aker in Siidermannia, to which is related the sappkirine; the 
brown, often found in crystals of considerable dimension, from New 
Jersey; and the chlorospinel of Rose, in which a portion of the alumina is 
replaced by oxide of iron, from Slatoust, Siberia;— the savphirine, &c.; 
