50 natural history. (Minerals.) [north 
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 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 ), 
which occurs at Huelgoet in Brittany only, is essentially 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. 
—jRock 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 
or morion, cairngorm, citrine, &c. ; specimens of rock crystal enclosing 
various substances, such as rutile, brown iron-stone, micaceous iron, 
aeicular antimony, actinolite, asbest, chlorite, &c. ; groups of rock 
crystal; some specimens of rock crystal in a wrought state are added. 
Case 21. Common quartz: among the specimens of this widely-dif¬ 
fused substance, which offers such a great variety in its external aspect, 
the more remarkable are the hacked, corroded, and cellular quartz 
from Schemnitz, as also the pseudomorphous or supposititious crystals, 
principally derived from modifications of calcareous and fiuor spars; 
and, with regard to colour, the blue quartz (called siderite quartz ), from 
Salzburg, and the rose or milk quartz, which are both used as ornamental 
stones;— fibrous quartz;—-flexiblesandstone ( itacolumite ) from Brazil*, 
China and the East Indies fetid quartz, from Nantes ;— iron-flint. 
In this Case is also placed a suite of varieties of stalagmitic quartz 
{quartz-sinter, pearl-sinter , geyserite, fiorite ), the more remarkable of 
which siliceous concretions are those deposited by the hot springs of 
the Geyser of Iceland, those of Santa-Fiora in Tuscany, and par¬ 
ticularly those of Luzon, one of the Philippine Islands. To these are 
added specimens of the cerauvian sinter or those enigmatical siliceous 
tubes which were discovered in the sands of the Senner Heath in the 
County of Lippe (where, on account of their probable origin, they are 
called blitz-rohren , or lightning tubes, from which name those of 
fulgurite , ceraunian sinter, astraphyalite, are derived), at Drigg on 
the coast of Cumberland, and lastly, by the late Capt. Clapperton 
(see Append, to his Journal), near Dibbla in the Tuarick country, 
Africa, from which localities specimens are here deposited.—The 
hyalite, a mineral related equally to stalagmitic quartz and opal;—the 
* Large specimens of flexible sandstone are placed in a table in the middle of the 
room, opposite Case 21: they are from the mountains of Itacolumi, near Villa 
Ricca, in Brazil, and were presented by His Excellency Viscount Strangford. 
