Gold Specimens from Bendigo. 163J 



quartz crystals continues for a longer period than required for 

 the gold crystals. The tremendous crystallising pressure of the 

 quartz, which is sufficient to force apart the walls of the vein^ 

 may then be partially directed against the growing crystals of 

 gold, modifying them in the same way that gold is hammered 

 in the production of gold leaf. In this case the final result is a. 

 sheeted interlacing of gold with quartz, ankerite, and other 

 minerals, with an appearance that has often suggested the in- 

 filtration of secondary gold in cracks in a quartz vein. 



The specimen illustrated in Fig. 1 came from the Constella- 

 tion saddle reef above the 622 feet level. It shows a black slaty 

 seam, partly mixed with ankerite, pursuing its normal tortuous- 

 track through the quartz. Several particles of gold, pyrite and 

 galena occur in this specimen along this carbonaceous seam,, 

 including a well-formed cube of pyrite. Particles of gold are 

 embedded in the cube of pyrite, and appear to have formed the 

 nucleus of the crystal. 



Another specimen, occurring near this cube in the same saddle 

 reef, shows an intimate mixture of gold, galena and pyrite. The 

 mixture borders upon a carbonaceous lamina, visible on the side 

 of the specimen, but which is not revealed in the photograph 

 (fig. 2). The photograph illustrates a sliced surface of the 

 specimen on which only a few fragments of carbonaceous matter 

 are showing, but pyrite (P), gold (white), and galena (Ga) 

 are distinguishable. The mass of pyrite is embedded in quartz,, 

 but at the same time it is broken by veins of quartz, galena 

 and gold. The gold appears not only as nuclei of some of the 

 pyrite, but also as a network of veins in the pyrite, and in the 

 galena. 



Without consideration of the process of formation of the 

 vein, the petrographical relations of the quartz and pyrite in 

 these two specimens would indicate that — (1) pyrite crystal- 

 lised before gold, and (2) that gold crystallised before pyrite. 

 The apparently contradictory character of these conclusions 

 appears to me to disappear when the vein is viewed as a slow 

 and steady growth, in which the quartz and each other mineral 

 are slowly and continuously deposited from the initial stages 

 up to the final stages of the formation of the vein. The gold,, 

 pyrite and galena are localised in the quartz in these instances, 

 partly by the precipitating action of the slaty residues, and, in- 

 a growing mixture of gold and pyrite, some of the pyrite may 



