54 
ECONOMIC GEOLOGY 
its value to such great depths. The ore-body has the shape 
of a flattened pipe with an average thickness of 10-12 feet., 
a maximum of 33 feet, and a width of usually less than 600 
feet, though in places of 1000 feet. It is in a bed of chloritic 
schist which is probably altered calcareous clay. The bed is 
vertical, and the pipe of ore lies along it at an angle of 45° 
to the horizontal. The ore consists of sulphides, especially 
pyrite, pyrrhotite, and arsenopyrite, with a little chalco- 
pyrite, and a matrix of siderite, quartz, dolomite, and calcite, 
with some carbon and fragments of the chloritic schist. 
The gold is rarely seen as it is present in the arsenopyrite. 
The ore was foliated after the mineralization, and the sparse 
vein-quartz is barren. There is no evidence of much earth- 
movement, such as faulting, and no pug along the ore. The 
lower levels are quite dry and the lode has no deep-seated 
minerals, such as tellurides or tourmaline, There is also no 
clear evidence of the infiltration of solutions, and the ore 
has maintained its value as deep as it has yet been followed. 
This lode was probably a placer containing alluvial iron 
oxide and fine-grained gold ; when the sediments were foliated 
into chloritic schist, the iron minerals were converted into 
sulphides, and the gold dissolved and redeposited with the 
arsenopyrite. This view is consistent with the continued 
richness of the ore in depth, its mineral character and micro- 
scopic structure, and absence of infiltration channels.