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* CLINKSTONE. 87 The fragments are indeterminate angular, and often slaty. It occurs in columnar, globular, and tabular distinct concretions. It is strongly translucent on the edges. It is intermediate between hard and semi-hard. It is rather easily frangible. It is brittle. In thin plates, it emits, when struck, a ringing sound. Specific gravity, 2.575, Klaproth. Chemical Characters. It melts before the blowpipe into a grey-coloured glass, but with more difficulty than basalt. Constituent Parts. Silica, - - 57.25 Alumina, - - 23.50 Lime, - - 2.75 Natron, - - 8.10 Oxide of Iron, - 3.25 Oxide of Manganese, 0.25 Water, - - 3.00 9S.10 Klaproth, Beit. b. iii. s< 243. Geognostic Situation. This mineral occurs principally along with rocks of the tloetz-trap series. When it forms part of a hill or range of hills, with wacke, basalt, and greenstone, we generally find it resting on the basalt or wacke, and covered by the greenstone. Geographic