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AGE OF METALS. tng. This gold is the pureft found in Tranfyl- vania ; a circumftance fufficiently indicating, that it belongs to a different, and confequently earlier formation, than the ufual Tranfylvanian native gold, which occurs there in clay-porphyry, grey- wacke, and grey-wacke flate, and belongs to the brafs-yellow variety, from the confiderable alloy of filver which it contains. In thefe ftream-works the nigrine is obtained at the fame time with the gold, and comes to us intermixed with grains of rutile, precious garnet, kyanite, and common fand ; which renders it extremely probable, as Dr Mitchell remarks, that this foffil, alfo, is a native of primitive mountains #. e. Iferine.—Hitherto this foffil has been found only in the high Riefen mountains, which feparate Silefia from Bohemia, near the origin of the Ifer, difperfed through the granitic fand which forms the bed of that river. To what order of rocks it owes its origin, is uncertain ; but its near affinity to iron-fand, which is exclufively an inmate of the neweft floetz-trap formation j and the certain ty that this formation was formerly fuperftratified, at a great elevation, on the Riefen mountains, (as the remains which form the Buchberg, and occu py the Schneegruben, fufficiently teftify), renders it highly probable, that this foffil alfo may belong to that formation ; and confequently dates its ori gin * Vide Mitchell, in Irifh Tranfaftions,