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7* CHRYSOLITE FAMILY. olivine are smooth, those of chrysolite streaked, shining, and glistening; the lustre of olivine is intermediate be tween resinous and vitreous, but that of chrysolite is splendent and vitreous; the fracture of olivine is imper fect conchoidal, or imperfect foliated, whereas that of chrysolite is perfect conchoidal; olivine often occurs iri distinct concretions, chrysolite never; olivine is trans lucent, passing into semi-transparent, chrysolite is trans parent ; olivine is very easily frangible, chrysolite easily frangible; olivine is softer than chrysolite; and the specific gravity of olivine is 3.225 to 3.265, that of chry solite 3.34 to 3.4. b. Olivine is nearly allied to Augite: this alliance is not so much a consequence of agreement in external cha racters, as rather a similarity in geognostic relations. Both species occur in the same species of rock, and the one seldom without the other ; and large masses and grains of olivine sometimes contain small angular grains- of augite, which take, as it were, the place of single dis tinct concretions,—a fact which shews their mutual affi nity. It is distinguished from Augite by its paler colours,' external shape, kind of lustre, fracture, superior trans parency, and its inferior hardness and weight. c. It is distinguished from Common Green Garnet, by 1 its greater transparency, inferior hardness, and weight, and geognostic situation. 2. Leonhard, Iteuss, and others, divide this species into two subspecies, named Conchoidal and Foliated; but Karsten has shewn that the foliated subspecies is augite. 3. It is named Olivine, from its olive-green colour. 4. It frequently decays, or falls into an earth, which wiuch resembles iron-ochre. When it begins to exhibit on