Pch-u((>(ji/ ((till (rn>lo(/>/ of QiieeustoiVn. 14/ 



after ilmeuite, and iIil' I'diinat ion of calcito and a little seriidle. 

 (.'heinieal chan^'es in the roek are sliglit. (2) Alteration i)y the vein 

 .solutions. The chief effeets are extensive developinent of seiieite 

 after felspar, and of carbonates, pyrites and niuseovite. after 

 chlorite and remaining hornblende, ('lieniical migrations are prt,- 

 bably great. The relative proportions of the alkalies, foi- in.staneo. 

 are reversed. 



The latter part of the j»a))er deals with certain characteristics of 

 an important, but now forgotten, gold field. Of particular inteiest 

 was the occurrence of large nuggets at One Tree Hill, clearly derived 

 frotii the Swedish reef which was known to be nuggety near the sur- 

 face. 



In concluson. the writer wishes to record his indebtedness to Mi-. 

 A. M. Howitt. of the Victorian Geological Survey, for drawing his 

 attention to the record of alluvial nuggets found on this field ; 

 to Ml', (.'hapman, foi' identification of a few fossils; and to Messrs. 

 Tallin and Mann, of the Imperial College of Science, Lond(tn. and 

 the Melbourne University, Geological Departments, respectively, 

 for numeious rock sections, and Professor Skeats and the Secre- 

 tai-y for Mines of Victoria, for help in obtaining Parish Plans of 

 the a lea. 



EXPLANATION OF PLATE XIX. 



Eig. 1. — Microphotograph of <,)uaitz Diorite, Caledonia Mine, 

 <^ueenstown, x 10, ordinary light. The black areas 

 represent ihnenite, and tlie striated phenocryst is horn- 

 blende partially altered to light coloured chlorite and 

 epidote. 



Eig. 2. — .Microphotograph of (,)uartz Diorite. Cale<Ionia Mine. 

 Queenstown, x 20, crossed nicols ; showing well-zoned 

 plagioclase phenocrysts. 



Eig. ;}. — Microphotograph of highly metasomatically altered 

 Diorite. near a quartz vein. Caledonia .Mine. <^)ueens- 

 town, X 16, ordinary light. Q=quartz. E = highly 

 sericitised felpar. M = niuseovite and carbonate replacing 

 chlorite after hornI)lende. P = pyrite. As = arsenopyrite, 

 S =stibnite. 



Fig i. — Microphotograph of metasomatically altered Quartz- 

 Felspar-Porphyry. One Tree Hill, X 11, ordinary light; 

 .showing phenocrysts of colourless quartz. idiouKjrphie 

 sericitised and carbonated orthoclase, and rectangular 

 sections of niuseovite aftei- I)iotite. 



