Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/362

 III. On the Occurrence of Gold.

All the rocks in which gold has recently been discovered in the County of Hastings are comprised within the Laurentian area, known as the Quinte Gold-mining District. The first discovery of the precious metal was made in 1866, during an unsuccessful search for copper ores. Superficial indications of the occurrence of copper in the township of Madoc had previously led to the prosecution of irregular workings in several localities ; but none of the explorations had been characterized by any measure of success. At length, however, a specimen was obtained from one of these so-called mines which, although at first mistaken for native copper, was soon found to be native gold. Stimulated by this discovery, further search was prosecuted ; and at the locality which subsequently became famous as the " Richardson Mine," a considerable quantity of free gold was discovered in two pockets, or irregular cavities, at a depth of about 15 feet below the surface. Considerable interest attaches to this mine, not only on account of the large amount of gold which it yielded within a very short space of time, but more especially on account of the peculiar conditions of association under which the metal occurred.

The Richardson Gold Mine is situated on the eighteenth lot of the fifth concession in the township of Madoc. The surrounding rock consists of an epidotic and chloritic gneiss, enclosing a bed of steatitic schist, and associated in certain places with a ferruginous dolomite. A peculiar character is given to this dolomite by the local occurrence of a black carbonaceous substance which, in external characters, bears considerable resemblance to a lignite, but which is regarded by Dr. Sterry Hunt as probably an altered form of bitumen. It occurs imbedded in the dolomite, in small irregular fragments, which break with a conchoidal fracture, and present a pitch-black colour and a resinous lustre. Heated in the open air, it readily ignites, burning with little or no flame, and leaving a residue which, in a specimen examined by Dr. Hunt, consisted of " carbonate of lime, with some siliceous and ferruginous matter, including a quantity of gold."

This friable carbonaceous substance, in association with ochrey oxide of iron, incrusted the walls of the gold-bearing pockets of the Richardson Mine, and formed the matrix through which the metal was chiefly disseminated. It would appear that these pockets are merely expansions of a fissure running along the plane of bedding between the highly inclined rocks of the surrounding country. The contents of these cavities have evidently been derived from the decomposition of the surrounding dolomite; for that rock, as seen by the specimens exhibited, contains the disseminated carbonaceous matter, together with free gold, whilst it appears to be sufficiently ferruginous to yield the oxide of iron on decomposition. Whether the carbonaceous substance has, by its reducing action, played any part in the genesis of the gold is a chemical question on which the writer is not prepared to enter ; but their intimate association in this mine is