448 Transactions.— Geology. 
The presence of gold in these reefs appears to depend upon a variety of 
circumstances which are not yet thoroughly understood ; I may, however, 
mention a few essentials which have been observed. The first of these is 
that the reefs should be passing through moderately hard compact country, 
and where this is traversed by thin black pyritous veins which junction 
with the reef, the character of the country may be looked upon as more 
favourable. Where any reefs are found passing through this class of 
country they are generally more or less auriferous, and this is specially 
noticeable in the large reefs of the district. There are, however, in addition 
to the large reefs, innumerable small leaders, from ;, inch thick up to a 
few inches, which, while following approximately the same strike as the 
other reefs, are as a general rule somewhat steeper; and where these junc- 
tion with the main reefs in favourable country, very rich deposits of gold 
are frequently met with. Besides these hanging-wall leaders there are also 
many droppers from the foot-walls of the reefs in which also rich gold is 
often found, and they give one the impression of being leaks, if I may use 
the term, from the main reef, by which some of the gold has escaped. 
The character of these deposits points most conclusively to the fact that 
the greater quantity of the gold in the reefs was deposited from solution, 
and the fact of the junctions of different leaders making the gold, leads one 
to believe that it was only where two streams, carrying the necessary ingre- 
dients in solution, met and mingled that any precipitation of gold ensued 
and a deposit of the precious metal was formed. 
There are many other points bearing upon the behaviour of the reefs 
which are of great interest, but which it is not my province to discuss here. 
That all the gold in these reefs is not derived from the same source, is 
I think, however, apparent, for that which is crystallized or occurs in 
dendritic forms, would owe its origin to super-heated steam, in the same 
manner as the last described set of rocks, and the description of gold with 
native arsenic from the Kapanga Mine, Coromandel, which will be foun¢ 
under the head of arsenic, offers a very striking illustration of this. 
With regard to alluvial gold but little need be said. The principal 
alluvial fields are those of Otago and the West Coast, with some smaller but 
still important ones in the Nelson district, and the alluvial gold partakes 
of the same characters as that obtained from the reefs. Large nuggets are 
rare, indeed the largest which has been obtained is one from Rocky River; 
Collingwood, weighing 10 ozs., and another from the same locality weighed 
8ozs. These are mentioned by Dr. vy. Hochstetter, (New Zealand, p. 100.) 
Gold is also obtained from what are known as the Cement workings, 
sh Tosmeles, tak ceorelen These cements consist of te coat 
have been ‘ 
belie 
— 
eeerrane 
ae en tee 
