GALLERY.] 
NATURAL HISTORY. 
(Minerals.) 
67 
Journal,) near Dibbla in the Tuanck country, Africa, from which 
local: ties specimens are here deposited— The hyalite, a mineral related 
equally to stalagmite quartz and opal —the haytorite, a pseudomor- 
phous 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 
actmote - — as also some varieties of the cats eye (mostly from Cey- 
lon), m which the chatoyant lustre is generally produced bv 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 ; among these are the re- 
markable 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 ; flint con- 
taining water, &c. 
The remainder of the contents of this and the whole of those of the 
following Case relate to calcedonic substances. Among the specimens 
of common calcedony the most remarkable are, the smalt-blue variety 
trom Felsobanya in Transylvania, crystallized in obtuse rhombohedrons ; 
the blanched and stalactical calcedony from Iceland; the splendid speci- 
mens from Cornwall, especially from Trevascus mine, &c. ; the botryoi- 
dai, from Feroe ; the large hollow geodes from Oberstein ; nodules, 
enclosing water (enhydrites), from Monte Berico, near Vicenza, where 
they occur m volcanic rocks, &c. 
Case 23. Calcedonic substances continued : cut and polished pieces 
of calcedony with red and black dendritic and other figures, called 
mocha-stones; varieties with white, brown, and black, straight or 
curved lines, some of which were probably among the substances of 
which the costiy vasa murrhina of the ancients were made ; red and 
yellowish varieties of calcedony called carnelian Plasma, —Heliotrope, 
an intimate mixture of calcedony and green earth, which, when con- 
taining disseminated particles of red jasper, is commonly termed blood- 
stone — I he beautiful and much esteemed variety of calcedony called 
chrysoprase, hitherto only found at Kosemutz in Silesia, and which 
owes its colour to oxide of nickel, as does the green siliceous earthy 
substance, named pimelite, which accompanies it. To these are added 
specimens of some varieties of the siliceous compounds called agates, 
m which calcedony, carnelian, amethyst, and heliotrope generally form 
the predominant ingredients, combined in straight, or more or less 
curved and concentric or zigzag delicate lines, imitating coloured de- 
signs of fortifications, &c. : among these may be particularized the beau- 
tdul agate-nodule from the trap formation of Central Asia, presented 
by C. Fraser, Esq. r 
Case 24. . One half of this Case is occupied by the different 
varieties of jasper, . such as they are enumerated by Werner, viz. the 
globular or Egyptian jasper , found chiefly near Cairo, in rounded 
pieces, which do not owe their form to rolling, but are probably of 
organic origin : when cut and polished they exhibit various fanciful 
delineations (one of the specimens in the table represents on its 
