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110 I DOLOMITE FAMILY* Geographic Situation. It occurs along with galena, and other ores of lead, in the lcad-mines of Lead Ilills and Wanlockhead in La narkshire ; in the mines of Cumberland, Northumberland, and Derbyshire. On the Continent, it is found in Nor- way, Sweden, Saxony, Suabia, France, Hungary, and Transylvania. Observations. 1. It is distinguished from Calcarcous-spar, with which it has been confounded, by its colour-suite, inferior trans parency, perfect pearly lustre, greater hardness, and higher specific gravity. It also in general effervesces less briskly with acids than calcareous-spar. 2. The straight lamellar variety has been mistaken for Heavy-spar, from which, however, it is distinguished, not only by its inferior weight, but also by its concretions being very closely aggregated, wdiich is not the case with heavy-spar. 3. On exposure to the air, it changes, first to a light, then to a dark brown, bordering on black: hence the name Broivn spar, given to it by Werner. Second Subspecies. Fib rous Etown-Spar. Fasriger Braunspath, Werner. Fasriger Braunkalk, Ren,is, b. ii, o. s. 325.—Fnsriger Braunspath, Such. lr th. s. (>2<). Id. Mohs, b. ii. s. 121. Id. Leonhard, Tabel. s. 35. Id. Karst. Tabcl. s. 50.—Fasriger Braunkalk, Lenz, b. ii. s. 722. Id. Okcn, b. i. s. 3yl. External Characters. Its colours are reddish-white, flesh-red, pearl-grey, and yellowish-
