30 On the Geological Distribution of Gold. 



Only in one locality a deposition of polishing slate, the pro- 

 duce of Infusoria, has been found by the writer, resting on 

 the auriferous detritus, and being of 25 feet thickness. 



In California, the auriferous strata are seen on the bed- 

 rock, with great accumulations of well-rounded gravel and 

 stone, with rough sand, also arenaceous clay -beds cover to great 

 depth the gold-bearing materials, which occasionally are mixed 

 with clay. Many auriferous layers are covered with calcare- 

 ous conglomerates of fragmentary, angular rocks (there termed 

 " lava !") very compact and hard, occupying a thickness of 

 upwards of one hundred feet. In some localities, the first 

 and auriferous stratum resting on the bed-rock, consists of 

 pebbles and sand, cemented together with ferro-siliceous 

 clay and forming a hard mass several feet thick. 



In Australia, the diluvial auriferous detritus is generally 

 found to consist of sand and small angular fragments of 

 quartz of a yellowish white hue, the strata being more or less 

 argillaceous, and frequently all the deeper deposits consist of 

 more clay than sand, always with partly angular and partly 

 rounded fragments of rock, and more or less quartz-debris. 

 The old outlets or channels, from the time of denudation, ex- 

 isting along the cleavage of the schists and furrowed in a very 

 irregular direction, are found to the depth of nearly four hun- 

 dred feet. The auriferous detritus, consisting mostly of plastic 

 clay, with some gravel and sand, occupies a varied thickness 

 of from a few inches to several feet. At an inferior depth, 

 i. e., at the higher portion of the channel, a stratum of basalt, 

 about 50 to 70 feet thick, covers the auriferous sandy clay; 

 and, in proportion, as the depth of these channels increases, 

 the basalt-beds augment; and at about the depth of 400 

 feet, four distinct layers of basalt are found, between each 

 of which, diluvial matter marks the lines of division. This 

 part of the world only has shown that a volcanic production 

 covers the fluvial detritus, thus most carefully concealing 

 the treasures of the epoch. (Ballarat, &c, Victoria.) 



In some localities the auriferous stratum consists of sand 

 and gravel, cemented together with a ferro-siliceous clay, 

 forming a perfectly compact, hard mass, of a light-brown 

 colour.* 



Where the trap or basalt does not constitute the superior 

 strata of the auriferous drift, a more or less argillaceous and 

 well-pulverized detritus furnishes the layers by which the 



* The process of stamping is required for disengaging the gold particles 

 from the conglomerate. 



