NATURAL HISTORY. 
166 
[north 
mocha-stones; varieties with white, brown, and black, straight or 
curved lines, some of which were probably among the substances of 
which the costly vasa murrhina of the ancients were made; red and 
yellowish varieties of calcedony called carnelian—Plasma _ Heliotrope, 
an intimate mixture of calcedony and green earth, which, when con¬ 
taining disseminated particles of red jasper, is commonly termed blood¬ 
stone.—The beautiful and much esteemed variety of calcedony called 
chrysoprase, hitherto only found at Kosemiitz in Silesia, and which 
owes its colour to oxide of nickel, as does the green siliceous earthy 
substance, named pimelite, which accompanies it. To these are added 
specimens of some varieties of the siliceous compounds called agates , 
in which common calcedony, carnelian, and heliotrope generally form 
the predominant ingredient. 
Case 24. One half of this Case is occupied by the different 
varieties of jasper, such as they are enumerated by Werner, viz. the 
globular or Egyptian jasper , found chiefly near Cairo, in rounded 
pieces,(which appear not to owe their form to rolling, but to be original, 
and produced by infiltration ;—the riband-jasper or striped jasper, the 
finest varieties of which are found in Siberia;—the variously-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 substances (mostly 
hydrates of silica), viz., specimens of the noble opal, which owes its 
beautiful play of colours to a multiplicity of imperceptible fissures in its 
interior ;—the sun-opal, or 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 property of becoming transparent when immersed in water, 
is called hydrophane, or oculus mundi;— wood-opal, or opalized wood ; 
-jasp-opal, referred by some authors to jasper;—the menilite, liver or 
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 the silicates of magnesia. 
To the former belongs the table spar or wollastonite from Mount Ve¬ 
suvius, Nagyag, &c. The silicates of magnesia comprehend several of 
the minerals placed by Werner in the talc genus :— steatite, the more re¬ 
markable varieties of which are, that of yellowish green colour from Green¬ 
land, and that from Gdpfersgriin in Baireuth, 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 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 lime¬ 
stone, the verde antico and some other fine green marbles ; among the 
varieties of the common serpentine, the best known are those from 
