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S 62 * ■Aggregates. Thefe fandftones have been found cryftallized in rhomboidal tables fuperimpofed one upon the other, and thus forming a fort of pyramid, orin rounded mafles. The fandftone of Fontainbleau is a remarkable fpecirherTöf ■ this kind, its colour is grey for the moft part, though fome yellowifh and reddifh are found from a fmall contamination of iron. Hardnefs, 9. Sp. gr. before penetration with water, is 2,5739; and after penetration, 2,6111. It contains by the experiments of Mr. Lafone 62,5 per ct. filex, and 37,5 mild calx; he remarked that it gave out very little air by heat. The Cos, Quadrum, ofWallcrius, feems to be of this fort. Another cryftallized ftoneof this fort was found in the territory of Juliers, its colour reddifh grey, but invefted with a red ochry duft. Its fradture fmall grained foliated. Sp.gr. 2,533. ^ ts f° rnl quadrangular and tabular. By the analyfis of Mr. Weftrumb, it contains 70 per ct. of filex, 15 of mere calx, 4 of fixed air, and 10 of calxof iron. 2 Chy. An. 1789, 31. Hefe it is remarkable that the calx contained nearly more by the one half fixed air than itufually dqes. Baron Born mentions , a flefh-coloured fpar vifibly mixed with quart^, whofe fra&ure prefents a lurface concentrically ftfiated, and whpfe denfity is confiderable ; it effervefces with acids, and gives fire with fteel. It contains manganefe, to which both its colour and denfity ^re owing. 31 Roz. 22. Calcareous marls that contain lefs than 33 per ct. of mild calx, the remainder beilig sicher v. holiy filiceous, orat leaft containing fo little ar- gill as not to form a brick when burned, may b.e annexed to this clafs. Of this fort is the light grey