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DIOPSIDE. 65 Geognostic anil Geographic Situations. It is found in the hill of Ciarmetta in Fiedmont; also in the Alp of La Mussa, near the town of Ala, in veins, along with epidote or pistacite and hyacinth-red gar nets ; and in the same district, in a vein traversing ser pentine, along with prehnite, calcareous-spar, and iron- glance, or specular iron-ore. It is said also to occur at St Nicolas, in the Upper Valais. Observations. 1. Tills mineral was discovered by Dr Bonvoisin, who formed it into two species, named Alalite, and Mussite: the white-coloured and massive varieties, and those crys tallised in the form N° 2. he refers to alalite; the green, with scopiformly aggregated crystals, and radiated frac ture, he considered as mussite. Ilauy having ascertained that mussite and alalite have the same primitive form, ranged them in the system as one species, under the name Diopside; afterwards, he ascertained that the primitive torm of diopside did not differ from that of augite, and consequently, in conformity with his system, abolished the diopside species, and arranged it with augite. Al though the primitive form of diopside and augite be alike, we are still inclined with Werner to consider them as distinct species. Diopside differs from Augite in co lour, crystallization, fracture, its streaked surface, thin and straight lamellar concretions, transparency, hardness, and geognostic situation *. Vol. II. E 4. Chrysolite. * The only specimens I have ever seen of this mineral, arc those in my possession, sent me by Sir Hewland of London.