gallery.] natural history. (Minerals.) 69 
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 colours, from deep orange yellow to nearly untinged; 
found in the trachytic porphyry of Zimapan, in Mexico;—the common 
opal, a translucent white variety of wdiich, 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 w r ater, is called hydrophane, 
or oculus mundi;— wood-opal, or opalized wood, chiefly from Hungary; 
—jasp-opal, referred by some authors to jasper;—the menilite, or liver 
opal, found at Menil-le-Montant., near Paris, in a bed of adhesive slate, 
a specimen of which is added;—the red opaline substance called 
quincite , from St. Quintin and from Mehun in the Department de 
Cher, is common opal tinted, as it is supposed, by organic colouring 
matter, in the same manner os the magnesite occurring with it in the 
fresh water limestone of that part of France. 
In the two next Cases are placed the Silicates with one base. 
Case 25 contains the silicates of lime and some of the silicates of 
magnesia and of alumina. To the former belong the table spar or 
wollastonite from Mount Vesuvius, Nagyag, &c., and the ohenite ; 
perhaps also the alumocalcite of Breithaupt, before considered as de¬ 
composed opal, from Eibenstock, Saxony. 
The silicates of magnesia comprehend several of th& minerals placed 
by Werner in his talc genus:— steatite , or soapstone, the more interest¬ 
ing varieties of which are, that of yellowish green colour from Greenland, 
and that from Gdpfersgrlin in Franconia, with small crystals of other 
mineral substances, especially quartz, converted into, and forming part 
of the massive steatite ; variety called chalk of Bria^on ;— kefiekil , or 
| meerschaum, from Natolia, of which the well-known pipe-bowls are 
! made, and that from Valecas in Spain ;—also a related substance, 
called heffekillite by Dr. Fischer, who discovered it. in the Crimea;_ 
| the lithomarge, or steinmarh, has been associated with steatite, although 
; most of its varieties are silicates of alumina: the more remarkable of 
| which are, that of a reddish-yellow colour in porphyry, from Rochlitz, 
j and the fine purplish-blue variety from Planitz ( teratolite , formerly 
I called terra miraculosa Saxonica), &c.— serpentine, the purer varieties of 
which (generally hydrates) are called noble serpentine : they constitute, 
I in combination with primitive lime-stone, the verde antico and some 
i other fine green marbles; crystallized serpentine, from Snarum, in Nor¬ 
way ; — among the varieties of the common serpentine, those best known 
j are from Baireuth and from Zdblitz in Saxony, where they are manu- 
! factored into vases and various other articles: serpentine with embedded 
i garnets, magnetic iron-stone, asbest, &c..—Of other substances nearly 
related to serpentine in this Table Case we have, the hydrophite of 
| Svanberg; the picrolite • the antigorite; the villarsite, &c.—With these 
are also placed the metalloid diallage or diallagite, more commonly called 
scliiller-spar, from the Hartz, &c.; and some varieties of what is called 
bronzite and xanthophyllite _To the silicates of magnesia is also re- 
i ferred the olivine, a green granular substance, occurring chiefly in trapp 
rocks, as also in the cells of the meteoric iron of Siberia and Atacama 
(see Case 1): when in a pure state and crystallized it is denominated 
