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IRON-CLAY. 4. Iron-Clay. Eisenthon, Werner. Eiscntlion, Karslcn, Tabel. s. 38. Id. Steffens, b. i. s. 340. Id. Lenz, b. ii. s 614.—Eisenwacke, Oken, b. i. s. 366. External Characters. Its colours are reddish-brown, and brownish-red, pass* ing into a tint between yellowish-brown and laurel-berry- brown. It occurs massive, and vesicular, as the basis of some varieties of amygdaloid. Internally it is dull or glimmering. The fracture is small and tine-grained uneven. The fragments are blunt-edged. It is semi-hard, passing into soft. It is opaque. It is rather brittle. It is easily frangible. Tt is rather heavy, but in a middling degree. Geognostic and Geographic Situations. It occurs in beds, and in the form of amygdaloid, along with floetz trap rocks, in 1'ifeshire, island of Skye, and other parts of Scotland; and in the north of Ireland, as st the Giants Causeway, it is associated with rocks of the same nature. It also occurs in Iceland, Feroe Islands, and in the County of Glatz in Silesia. Observations. This species, which was first established by Werner, appears to be intermediate between wacke and basalt, and is distinguished from both by colour, Iracture, hard ness, (which is less than that ot basalt, but more than ol wacke,) and easy frangibility. XX. DOLQ*