72 . MINERALOGY. 
or a boro-silicate of lime. It is eminent for the beauty and perfection of its 
crystals. It is found in great abundance at Andreasberg, in compact 
greenstone, traversed by veins of compact dolerite, and having crystals of 
the mineral in its cavities; also in New Jersey, Connecticut, and the 
Michigan copper region. It crystallizes in the monoclinic system, its forms 
being the oblique rhombic prism (pl. 34, fig. 73) and its derivatives. 
fig. 6 is a group of datholite crystals from nature. This is a rare mineral, 
and of no practical application. 
2. Apophyllite. 
Apophyllite is one of the most beautiful minerals in nature. It occurs in 
veins and beds in primitive and amygdaloidal rocks in the Tyrol, Bohemia, 
the Hartz, Scotland, Greenland, Mexico, and North America. Its most 
usual crystal forms are represented in figs. 28, 37, 43. It sometimes occurs 
in crystals of various sizes, grouped together (fig. 17), the individuals 
forming acute square octahedrons. It is transparent, colorless ; or else, white, 
yellow, green, and rarely rose-red. The crystals have a very peifect 
cleavage in the direction of the basal plane, from which the mass may be 
_ diminished by sections, perpendicular to the main axis, producing square 
faces. The basal corners are almost always replaced by rhombic faces, 
striated in the direction of the primary axis. Apophyllite is silicate of 
alumina combined with silicate of potash. 
3. Olivine, or Chrysolite. 
This mineral is a silicate of magnesia with a slight admixture of protoxyde 
of iron, and rarely oxydes of manganese, chromium, nickel, copper, and tin. 
Olivine is widely diffused in small crystalline granules, and occurs in the 
cavities of most basalt. The larger crystals (or the noble olivine) are found 
in Bohemia and in Hungary, and are used for ornamental purposes. 
Chrysolite occurs of a green, brown, or red color. The crystals belong to 
the trimetric system, as in pl. 34, fig. 74. 
4. Picrosmine. 
This is a hydrous bisilicate of magnesia with a slight admixture of 
protoxyde of iron, and manganese, with a small amount of alumina; it 
occurs in a single deposit in Bohemia. _ It is opake, sub-transparent at the 
edges, iridescent, and of a vitreous lustre, and of various shades of green. 
From its cleavage, its crystallizations belong to the form of fig. 41. 
5. Chondrotite. 
This mineral, a silicate of magnesia, is found in New Jersey and 
elsewhere in the United States, in Finland, &c. It is transparent or 
translucent, of yellow, brown, reddish-yellow, green, or black color; and 
generally occurs in granules. ‘When heated it loses color, becoming, first 
black, and then white. Its crystallization is that of pl. 34, fig. 54, or 
monoclinic. 
6. Augite, or Pyrozene. 
This occurs finely crystallized in volcanic mountains, and in lavas, and 
forms an essential constituent of basalt and dolorite. It is dark green, 
brown, and black, sometimes light green and white, with a vitreous or 
resinous lustre, opake, or only translucent at the edges. The crystals 
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