NATURAL HISTORY 
55 
GALLERY,] 
varieties of jasper, such as they are enumerated by Werner, viz. the 
globular or Egyptian jasper , found chiefly near Cairo, in rounded 
pieces, which Jo not owe their form to rolling, but are, according to 
the opinion of some writers, produced by infiltration, or, what is 
more probable, are of organic origin ;—the riband-jasper or striped 
jasper, the finest varieties of which are found in Siberia;—the va¬ 
riously-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 sub¬ 
stances (some of them hydrates of silica), viz., specimens of the noble opal , 
which owes its beautiful play of colours to a multiplicity of otherwise 
imperceptible fissures in its interior;—the sun-opal , or fire-opal , ex¬ 
hibiting a suite of colour, from deep orange yellow to nearly untinged, 
from the trachytic porphyry of Zimapan, in Mexico ;—the common 
opal , a translucent white variety of which, appearing yellow or red 
when held between the eye and the light, is called girasol;—the semi¬ 
opal , agreeing in its principal characters with the common;—specimens 
of a variety both of common and noble opal, which, having the property 
of becoming transparent when immersed in water, is called hydrophane, 
or oculus mundi;— wood-opal , or opalized wood, chiefly from Hungary; 
-jasp-opal, referred by some authors to jasper;—the memlite , or liver 
opal, found at Menil-le-Montant, near Paris, in a bed of adhesive slate, 
a specimen of which is added ;—the quincite of Berthier, or red opal 
of Quincy, near Meudon in France, which, containing magnesia, is 
rather to be considered as a hydrous silicate of magnesia. 
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 wollastonite from Mount Ve¬ 
suvius, Nagyag, &c. ; perhaps also the alumocalcite of Breithaupt, be¬ 
fore considered as decomposed opal, from Eibenstock, Saxony. 
The silicates of magnesia comprehend 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, and that from 
Gopfersgriin in Baireuth, with small crystals of other mineral substances, 
especially quartz, converted into, and forming part of the massive 
steatite ; variety called chalk of Briam^on ;— heffehil , or meerschaum, 
from Natolia, of which the well-known pipe-bowls are made, and 
that from Valecas in Spain ;—also a related substance, called keffe- 
killite by Dr. Fischer, who discovered it in the Crimea ;— lithomarge , 
the more remarkable varieties of which are, that of a reddish yellow 
colour in porphyry, from Rochlitz, and the fine purplish blue variety 
from Planitz, formerly called terra miraculosa Saxonica, &c.— ser¬ 
pentine , the purer varieties of which (generally hydrates) are called 
noble serpentine : they constitute, in combination with primitive lime¬ 
stone, the verde antico and some other fine green marbles ; among the 
varieties of the common serpentine, the best known are those from 
Baireuth and from Zoblitz in Saxony, where they are manufactured into 
vases and various other articles; serpentine with embedded garnets, 
magnetic iron-stone, asbest, &c.-=—the marmolite of Hoboken in New 
Jersey likewise belongs to serpentine-With these is also placed the 
metalloid diallage or diallagite , more commonly called sckiller spar, 
from the Hartz, &c.; and, what appear to be varieties of the same, 
the bronzite and the xanthophyllite .—To the silicates of magnesia is 
