Silver deposits at Kongsberg. (The mineral assemblage of a native silver-cobalt-nickel ore type).

Abstract

The described deposits of the native silver - nickel - cobalt - arsenide type are found in a pre-cambrian series of the rocks, by far the greater part of which is made up of banded, dioritic and granitic gneisses. The described minerals have been deposited in narrow veins which are striking more or less E-W and are found to constitute a system of \"Fiederspalten\". The pressure under which the minerals have been deposited must be classed about 1000 atm., and the temperature has probably varied from 4-500 C to about 200 C. Calcite is predominanting in the veins. Sulphite is uncommonly rare. On p. 35 and p. 36 will be found graphic illustrations showing the relative quantities of the chief minerals. The various minerals have been described. The lamini-form crystals of native silver (p. 45) might be of special interest. Special interest also attaches to the curious way in which marcasite occurs, i.e. as primarily deposited mineral older than silver (p. 73). Marcasite must have been deposited under a comparatively high temperature from neutral or basic solutions. This is not in concordance with what is usually found, and it does not agree with the experimantal dates. - Anatase (p. 81) and datolite (p. 106) have not up till now been known from Kongsberg.