LONG 
GALLERY. 
Nat. Hist. 
122 
produced by infiltration;—the riband jasper or striped 
jasper, the finest varieties of which are found in Si¬ 
beria ; — the variously-tinted common jasper ; — the 
agate-jasper , found only in agate-veins, and the porce¬ 
lain jasper, produced by the action of subterraneous 
five on clay slate. The other half of this Case contains 
opaline substances (mostly hydrates of silica), viz., 
specimens of the noble opal , which owes its beautiful 
play of colours to a multiplicity of imperceptible fis¬ 
sures in its interior ;—the sun or Jire opal; —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 , agree¬ 
ing in its principal characters with the common;— 
specimens of a variety which, having the property of 
becoming transparent when immersed in water, is call¬ 
ed hydrophane, and vulgarly, oculus mundi;— wood 
opal, or opalized wood ;—j asp-opal, referred by some 
authors to jasper ;—the menilite, called also liver opal, 
found at Menil-Montant, near Paris, in a bed of ad¬ 
hesive slate, a specimen of which is added. 
In the two next Cases are placed the Silicates ivith 
one base . 
Case 25 contains the silicates of lime and those of 
magnesia. To the former belongs the table spar or 
wollastonite from Mount Vesuvius, Nagyag, &c.;—to 
the latter, several of the minerals placed by Werner 
in the talc genus : — steatite , the more remarkable va¬ 
rieties of which are, that of yellowish green colour 
from Greenland, and that from Gbpfersgriin in Ba- 
reuth, with small crystals of other mineral substances, 
especially quartz, converted into, and forming part of 
the massive steatite; variety called chalk of Briancon; 
.— keffekil , or meerschaum, from Natolia, of which 
the well-known pipe-bowls are made, and that from 
Valecas in Spain ;—also a related substance, called 
keffekillite 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 
