218 
AI.\iT[..\xr, 
irrstcni Ausfyalian Gcohujy. 
miik'i'lviiiji- causes that ]ia\x‘ more or u‘ss continuously in 
(|)eration fi'om the (aii-lit-st of geological limes. 
Mo(h‘i‘n wiatevs oa the iiatui'al history of ore <lej»osits call 
ntlention to 1lu‘ <-oiiiiection betnanm (juartz veins and acid ])eginatite 
dykes (tlu‘ off-shoots from the g'ranite) and their eonmiiinity of 
origin. In this connection it may ])0 ]udntod ont that my colleague, 
Mr. T. Hlatchford, in liis account of the geology of the Coolgardk- 
(loldfiehl, ])uhlished as far l)ack as the year 1899, d<‘scril)cd the 
Iransitioo from the normal granite of the field, thi’ough auriferous 
acid dykes to ])iire (|iiartz veins, distrihuted marginally with refer- 
ence to tiie mass e-f intrusive granite, whicli in this part of the 
(Vmtral Division covers such an extensive area. 
Tin' mining cmitre of Westonia, on the Yilgarii fu'ld, also 
fnrnislu's further important ovid(mce of the intimate relationship 
which exists ludweim tlie aurifm’ons rpiartz veins and the normal 
granit(‘ of the district. The <(uartz, which contains rows of fluid 
inclusions, is intimately assoeiated with felspar, l)oth of wliieh 
appear to have solidified at about the same time, and are merely 
varieties of a (|mn tz-felspar pegmatite, an acid differentiate of 
the granit(‘ magma. 
In this eonneciion it is intt-resting to note that the origin 
of g(dd-bearing (iiiartz vidns as a result of dTnh'rentiation from 
a granitie inagina is not bv anv means new. As far haek as the 
year IStil that Avell-knowii naturalist and mining eiigineer, Thos. 
Helt, first p(tinted out in a pajter eiititbnl ‘‘^Mineral \ (diis, an 
em|iiiry into their origin, foumUnl on a study of the Auriferous 
(Quartz Veins of Australia" that “(piai't/ vidns are as natnieilly 
jTodueed by granitic eru]dions as the acorn to the oak.” In the 
v('ar 18711 this author again a])])roaidied this subject and in a 
work entitled “ Tlu‘ Natui'alist in Nicaragua,” -where he managed 
a gold mine, he wrote: 
•VMiueraJ veins in granitie distriets oceiir in regular se([uences 
Tlune is also, sometimes, a ('(unphde gradation from veins 
(if perfectly (n-ystalUs('d granitic through others abounding in 
(piartz at the ex])ense of the other eoiistitiunits up to veins filled 
with }uire quartz.” 
It may thei'efoi'e be of interest to tho>sc engaged in tlu 
historical study of the researches into ore deposits to note that 
the eonception sixty-five years ago, of the idea of the source of cer- 
tain ty]ies of gold-bearing quartz veins as the end product of the 
differentiation of a granitic magma came about as a result of 
investigations into the goldfields of Australia, a fact whicli eminent 
geological writers on this subject have overlooked. 
