119 
ruby, oriental amethyst, oriental topaz, oriental emerald,) 
of the crystallized forms of which the principal modifi¬ 
cations are here deposited; and the common or imper¬ 
fect corundum from Bengal, Mysore, China, the Carna¬ 
tic (Werner’s diamond spar), Lapland, Piedmont, &c. 
As appendix to these are added, the fibrolite (bournonite 
of Lucas), one of the concomitant substances of the com¬ 
mon corundum of the Carnatic—the indianite of Bour- 
non, being one of the matrices of the same corundum—»the 
emery, which owes its hardness and consequent usefulness 
in polishing to an admixture of blue corundum.—The 
diaspore and the gibbsite: both hydrates of alumina. 
Aluminate of magnesia—the spinel: among its va¬ 
rieties is the blue spinel of Aker in Sudermannia. The 
ceylonite or pleonaste, and the automolite (also called 
gahnite) from Fahiun 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 substance called plomb gomme , from Huelgoet in 
Britanny : a hydrous aluminate of lead. 
The five following Cases contain the acid or oxide 
of silicium (silica, quartz), the numerous varieties of 
which, formerly considered as so many distinct species, 
are mostly indebted for their generally very striking ex¬ 
ternal 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 crys¬ 
tals, 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 or morion, cairngorm, citrine, &c.; speci¬ 
mens of rock crystal enclosing various substances, such 
as rutile, brown iron-stone, micaceous iron, needle-anti¬ 
mony, actinote, asbest, chlorite, &c.; groups of rock 
crystal; some specimens of rock crystal in a wrought 
state are added, such as Dr. Dee’s show-stone (see 
Walter Scott’s Demonology), &c. 
LONG 
GALLERY. 
Nat. Hist. 
Case 
