126 ORIGIN AND MODE OF OCCURRENCE OF GOLD-BEARING VEINS. 



also occurs under conditions which cannot be classed as belonging 

 to veins at all, being in fact impregnations .through certain rocks. 



As regards the origin of quartz veins and the minerals occurring 

 in them, much has already been said by those who have advocated 

 one or other of the theories of igneous injection, sublimation, 

 lateral secretion, etc., to account for their forming, and perhaps 

 it will be best to endeavour in these pages to see which of these 

 may be most applicable to the phenomena observed in connection 

 with the auriferous quartz veins of Australasia. 



It is in Victoria that auriferous quartz mining has been carried 

 on upon the largest scale in the colonies, and we find that the 

 veins, or " reefs " as they are locally called (which name is 

 synonymous with the term " ledge " used in America), may be 

 sub-divided under two or three classes, which embrace most, if 

 not all, of the special features of the gold veins in the colony. 



No better idea can be given of the general distribution of 

 auriferous quartz veins in Victoria than by quoting the following 

 extract from Mr. B rough Smyth's " Gold Fields and Mineral 

 Districts of Victoria": — "Whenever the surface of the schist 

 rocks is touched, — whether exposed as at Castlemaine and Bendigo, 

 or hidden under basalt, as at Ballaarat, or covered by tertiaries, 

 as at Sebastian and Wahgunyah, — we find auriferous veins of 

 quartz. The strata which they intersect are either altered or 

 present a low degree of metamorphism. The veins vary in 

 thickness from the sixteenth of an inch to 100 and 150 feet, and 

 some, — as thin as the paper on which these words are printed, — - 

 intersect soft mudstone and sandstone containing palaozoic fossils, 

 and in such a manner as almost to cut the fossils ; but the delicate 

 structure is not altered, nor are any of the interspaces filled with 

 quartz. 



" In some of the veins we find dense white milky quartz 

 homogeneous and breaking with almost a hackly fracture ; in 

 others, brownish and yellowish quartz, laminated, and resembling 

 jaspery quartz or hornstone, and showing a semi-conchoidal 

 fracture where broken ; again, we find veins of laminated quartz, 

 with pyrites and other sulphides intercalated, and pieces of blue 

 slate included in the laminations of the quartz ; and in many 

 places quite crystalline quartz, containing crystals of galena, 

 carbonate of copper, and iron pyrites, with free gold in the 

 interstices of the crystals and intermixed with the sulphides and 

 carbonates, and occasionally (not often) inf the bases of the 

 hexagonal crystals of quartz in moss-like aggregations ; not only 

 in the veins, but also in the casing of the veins does the gold 

 occur in lumps, crystals, and small particles, with rugged edges ; 

 and in the soft mud-stones at Kamarooka, thin plates of gold lie 

 in the planes of bedding of the rock." 



