Auriferous Q uartz-veins. 
121 
vapours, bearing in mind that the intensely -heated portion of the 
•earth's interior was then nearer to the surface than now, we have 
a set of conditions under which it is easy to conceive the forma- 
tion of siliceous veins, and the deposition with, or in them, of metals 
or minerals which had also previously been in a state of solution 
or volatility, though perhaps it may not be possible to reason out 
exactly the various forms of chemical action which were developed 
during the process. The late Sir R. Uaiutroo strongly advocated 
the theory that hydrothermal action arising out of deep-seated 
Plutonic action played an important part in the formation of 
quartz-lodes, and the deposit of their associated minerals. 
Assuming the above general main conditions as having been in 
existence, the infinite varioty of modes of occurrence of quartz- 
veins and associated minerals can bo reasonably attributed to 
them, though their action was evidently subject to local modifica- 
tion as regards degrees of intensity, or influenced by such 
mechanical forces as may have been contemporaneously in opera- 
tion. Thus we find that one quartz reef consists of white 
amorphous quartz ; another is more or less evenly laminated ; a 
third shows marked crystalline structure ; in a fourth, the lode 
contains oil one wall quartz of a different character to that 
occurring on the other, and the two kinds may be found to be 
separated by a clean parting or to merge into one another. Two 
or more of the foregoing features may bo found in different parts 
of the same line of lode. Gold or other minerals may be found 
near one wall more than the other, or any other of the phenomena 
encountered by the miner in connexion with quartz-veins may bo 
mentioned ; but there are none that I have seen or heard of that 
are not susceptible of explanation under the segregation and 
hydrothermal theory, allowing for different degrees of rapidity of 
action, intensity of heat, the predominance of certain minerals or 
vapours in one locality over another, and the various displace- 
ments due to further movements of the earth's crust which took 
place during or subsequently to the deposition of the vein-stones. 
It is not necessarily to bo inferred that the fissures to which 
the mineral waters determined were from the first as wide as the 
veins which now fill them. No doubt successive re-openings, 
caused by earth-movements, and enlargements of the fissures, 
effected by the passage of moving waters, enabled successive de- 
positions of quartz and other minerals to be produced, and to this, 
no doubt, may be attributed the circumstance of some particular 
band in a reef being usually more auriferous or more highly 
mineralized than another. As a rule, it has been observed that 
laminated or seamy quartz is usually more highly auriferous than 
that of a massive amorphous character; and the idea has sug- 
gested itself that the latter was formed quickly, there being an 
excess of siliceous matter present, and the metallic minerals not 
present in proportionate quantity; whereas, in the case of the 
