142 
LONG 
GALLERY. 
principal characters with the common;—spe¬ 
cimens of a variety which, having the pro¬ 
perty of becoming transparent when immersed 
in water, is called hydrophane, and vulgarly, 
oculus mundi;— wood opal , or opalized wood ; 
—jasp-opal, referred by some authors to jas¬ 
per ;—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 
with one base . 
Case 24 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 into the talc genus:— steatite , the 
more remarkable varieties of which are, that of 
yellowish green colour from Greenland, and 
that from Gopfersgriin in Bareuth, with small 
crystals of other mineral substances, especially 
quartz, converted into, and forming part of the 
massive steatite ;—the keffekil , or meerschaum, 
from Natolia, of which the well-known pipe- 
bowls are made, and that from Valecas in Spain 5 
—also a related substance, called keffekillite by 
Dr. Fischer, who discovered it in the Crimea ;— 
serpentine , 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 ; 
