66 
natural history. (Minerals.) 
[north 
replaced by oxide of iron, from Slatoust, Siberia the sapphirine , &c. ; 
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 
aluminafe 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 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 
or morion, cairngorm, citrine, &c. ; specimens of rock crystal enclosing 
various substances, such as rutile, brown iron-stone, micaceous iron, 
acicular antimony, actinote, asbest, chlorite, &c. ; groups of rock 
crystal ; some specimens of rock crystal in a wTought state are added, 
among which is Dr. Dee’s show-stone (see Walter Scott’s Demono- 
logy), &c. 
Case 21. Common quartz : among the specimens of this widely 
diffused 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 fluor 
spars ; and, with regard to colour, the blue quartz, called siderite, from 
Salzburg, and the rose or milk quartz , which are both used as ornamental 
stones; — fibrous quartz; — -flexible sandstone (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 those of 
Luzon, one of the Philippine Islands. To these are added specimens 
of the ceraunian sinter or those enigmatical siliceous tubes which vrere 
discovered in the sands of the Senner Heath in the County of Lippe 
(where, on account of their probable origin, they are called blitz-rdhren , 
or lightning tubes, from which name those of fulgurite , ceraunian 
sinter , astraphyalite , are derived), at Drigg on the coast of Cumber- 
land, and lastly, by the late Capt. Clapperton, (see Append, to his 
* 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. 
