gallery.] natural history. (Minerals.) 67 
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, actinolite, asbest, chlorite, &c.; groups of rock 
crystal; some specimens of rock crystal in a wrought 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 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 tluor 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 quartzflexible 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 par¬ 
ticularly those of Luzon, one of the Philippine Islands. To these are 
added specimens of the ceraunian sinter or those enigmatical siliceous 
tubes which w r ere 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 
haytorite , a pseudomorphous substance, being purely siliceous, but 
presenting the form of datolite the avanturino quartz , &c. 
Case 22 contains some more of the varieties of common quartz: 
prase , which appears to be an intimate mixture of that substance and 
actinolite;—as also some varieties of the cat's eye (mostly from Cey¬ 
lon), in which the chatoyant lustre is generally produced by nearly 
invisible fibres of amianth lodged in the quartzy mass.—Part of this 
Case is occupied by the siliceous substance called hornstone, divided 
into the conchoidal and splintery varieties, or chert ; among these are 
the remarkable pseudomorphous crystals from Schneeberg in Saxony, 
derived from various modifications of calcareous spar; also beautiful 
specimens of wood converted into hornstone, being the wood-stone 
of Werner ; hornstone balls from Haunstadt in Bavaria—Of flint, a 
well-known mineral substance, some interesting varieties are deposited; 
fine groups of stalactitical flint passing into calcedony; flint nodules 
containing water, &c. 
The remainder of the contents of this and the wmole of those of 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 
Ricea, in Brazil, and were presented by His Excellency Viscount Strangfo?d s 
