NATURAL HISTORY. 
105 
GALLERY.] 
viz., specimens of the noble opal, which owes its beautiful 
play of colours to a multiplicity of imperceptible fissures in 
its interior;—the sun ox 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 girasol; 
—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, and vulgarly, oculus mundi;— wood 
opal, or opalized wood ;—jasp-opal, referred by some 
authors to jasper;—the menilile, called also liver 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 those of mag¬ 
nesia. To the former belongs the table spar or wollasto- 
nite from Mount Vesuvius, Nagyag, &c. ;•—to the latter, 
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 Bareuth, with small crystals of other mine¬ 
ral substances, especially quartz, converted into, and form¬ 
ing part of the massive steatite; variety called chalk of 
Brian^on;— 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 keffe- 
killite by Dr. Fischer, who discovered it in the Crimea;— 
lithomarge, the more remarkable varieties of w T hich 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.— serpentine, the purer 
varieties of which (generally hydrates) are called noble 
serpentine: they constitute, in combination with primitive 
limestone, the verde antico and some other fine green mar¬ 
bles ; among the varieties of the common serpentine, those 
from Bareuth and from Zoblitz in Saxony are best known, 
where they are manufactured into vases and various other 
articles; serpentine with imbedded garnets, magnetic iron¬ 
stone, asbest, &c.—the marmolile of Hoboken in New 
Jersey likewise belongs to serpentine.—With these is also 
