ORES OF GOLD 
Ly, 
The propylitic origin of some gold explains the contro- 
VEIsy as to whether dykes enrich or impoverish adjacent 
lodes. A lode may be poor where in contact with a dyke 
and rich where separated from it, and vice versa. Such 
Apparent inconsistencies are explained by the AI Mine at 
Wood's Point in Victoria ; it consists of horizontal floors of 
Juartz in hornblende-porphyrite ; where that rock is normal 
the quartz is barren, but where the rock has been altered 
0 propylite the quartz-floors are auriferous. The gold is 
due to the Propylitization and not to the dyke. 
Tur CLassiFicaTIoN OF GoLp Ores 
Gold, owing to its ubiquitous distribution is found m2 
sreat variety of gre deposits. Excluding some of the 
important occurrences in contact deposits, and as an gh 0 
constituent in many sulphides the chief ores may be classifie 
as follows :— 
Sect, A—Primary_ 
L Gold-quarty F issure Lodes— 
(a) In sedimentary rocks, California ; Ballarat. S 
(5) In gneisses and schists. Mysore; Brazi 1 
Rhodesia, 
(¢) In volcanic rocks, Rocky Mountains ; New Zealand, 
(d) Pneumatoly tic, Cripple Creek; Passagem, Brazil, 
(I Isolateq Gold-quarts Veins i Saddle and Ladder Lodes— 
(a) Saddle-lodes, Bendigo; Nova Scotia. as. Vi 
(0) Ladder-lodes, Wood's Point + Little Bendigo, Vic- 
toria ; Berezovsk. 
{¢) Radial-lodes, Charters Towers, 
III. Impregnations and Replacement Bodies. Homestake, 
N. Dakota ; Alaska Treadwell ; Kalgoorlie, W. 
Australia ; Porcupine, Ontario. 
Sect. B—Secondary enrichments. Londonderry, W. Aus- 
tralia; Mt. Morgan, Queensiand, 
Sect, C—Ailuyigg Deposits— 
Surface drifts and leads. 
Deep leads, Victoria and Kanowna., 
Marine placers, 5 
Ancient placers. Rang Banket; Gold Coast ; . 
Dakota; Morro Velho, Brazil.