164 NATURAL HISTORY. [NORTH 
blood-stone.—The beautiful and much esteemed variety 
of calcedony called chrysoprase, hitherto only found at 
Kosemiitz in Silesia, and which owes its colour to 
oxide of nickel, as does the green siliceous earthy sub¬ 
stance, named pimelite , which accompanies it. To these 
are added specimens of some varieties of the siliceous com¬ 
pounds called agates , in which either common calcedony, 
carnelian, or heliotrope generally form a predominant in¬ 
gredient. 
Case 24. One half of this Case is occupied by the dif¬ 
ferent varieties of jasper, such as they are enumerated by 
Werner, viz. the globular or Egyptian jasper, found chiefly 
near Cairo in rounded pieces, which appear not to owe their 
form to rolling, but to be original, and produced by infil¬ 
tration;—the riband-jasper or striped jasper, the finest 
varieties of which are found in Siberia;—the variously- 
tinted common jasper ; —the agate-jasper , found only in 
agate veins, and the porcelain-jasper, produced by the action 
of subterraneous fire on clay-slate. The other half of this 
Case contains opaline substances (mostly hydrates of silica), 
viz,, specimens of the noble opal, which ow r es its beautiful 
play of colours to a multiplicity of imperceptible fissures in 
its interior;—the sun, or fire-opal ; —the common opal, a 
translucent white variety of which, appearing yellow or red 
when held between the eye and the light, is called girasoi; 
—the semi-opal, agreeing in its principal characters with the 
common;—specimens of a variety which, having the pro¬ 
perty of becoming transparent when immersed in water, is 
called hydrophane, or oculus mundi;— wood-opal, or opa- 
lized wood;—j asp-opal, referred by some authors to jasper; 
-—the menilile, liver or opal, found at Menil-Montant, near 
Paris, in a bed of adhesive slate, a specimen of which is 
added. 
In the two next Cases are placed the Silicates with one 
base . 
Case 25 contains the silicates of lime and the silicates of 
magnesia. To the former belongs the table spar or /vollasto- 
nite from Mount Vesuvius, Nagyag, &c.;—the latter com¬ 
prehends several of the minerals placed by Werner in the 
talc genus: — steatite, the more remarkable varieties of 
which are, that of yellowish green colour from Greenland, 
