NSTON. W. L. UGLOW AND Ww. A. JOH 556 es of minute lets of could have been formed only in zon Gold crystals and leaves or vein ones in quartz either near the sur- ut the limitation of the free gold to limonite occurs confines the quartz breccias, shattering of the quartz. gold may be formed in shear z face or at considerable depths ; b those parts of the veins in which possibilities of such occurrences in this area to fractured zones at or near the surface. The free gold, therefore, has been formed by processes which operated under conditions of oxidation near the surface. The hypothesis whic the occurrence of the free go unoxidized parts of the veirts W h is here advocated as an explanation of ld is that the gold content of the as and still is largely, if not en-~- tirely, confined to the sulphides, mainly arsenopyrite and pyrite; that the oxidation of these sulphides under near-surface conditions released the gold which passed into solution only to be precipitated in crystal and leaf form at short distances below in the belts of weathering and cementation. eration of such processes The conditions necessary for the op 1d in the veins to supply and for production of sufficient free go and disintegration of the the placers would be (1) deep weathering 2) the presence of solvents and precipi- veins and country rock, ( tants for gold, and (3) sluggish transportation by the streams. These conditions are fulfilled in the Barkerville area, which con- sists of a deeply dissected high-level plateau, the uplands being composed of remnants of a plain-like surface of erosion. Streams which formerly flowed at or somewhat below this plateau level must have been sluggish, for they occupied broad shallow valleys. The amount of material being carried by the streams was there- fore small, and rock decomposition with solution of the constitu- ents must have been the most important feature of the later phases of that cycle of erosion. There is little definite information available co agents of solution and precipitation of the gold in the veins of this area but it is certain that this action has taken place. As shown ncerning the