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52 CHRYSOLITE FAMILY. are not altered in the preceding figure, semi- truncated *. 11. Twin-crystal, in which the crystals are joined to gether by their broader lateral planes ■f', fig. 117. 12. Twin-crystal, in which the crystals intersect each other |, fig. 118. The crystals are all around crystallised, also imbedded, and superimposed: arc middle-sized, and small, seldom large. Internally it alternates from specular splendent to glis tening, and is resinous. The fracture varies considerably, being sometimes fine grained uneven, sometimes foliated, from imperfect to highly perfect foliated: this latter occurs principally in crystals, where it forms the longitudinal fracture. 1 he cross fracture is conchoidal. In the foliated fracture, a twofold slightly oblique angular cleavage is to be ob served. Besides these, a concealed foliated fracture oc curs. The massive variety occurs in distinct concretions, which are coarse and small granular, and very much grown together. It extends on the one side from translucent nearly to opaque; on the other nearly to transparent, as is paiti- cularly the case with the foliated and conchoidal. It scratches glass with difficulty. It is brittle. It is rather easily frangible. Specific gravity, 3.226, Ilauy. 3.286, Karstcn. Chemical * Pyroxene trioctonal, Hauy. -j- Pyroxene hemitropc, Hauy. $ Pyroxene hemitropc, Hauy.
