Microscopical Character of the Ore. — Adams. 
91 
sible to determine their exact limits owing to an impregnation of the 
rock about their edges, with the minerals of the vein. In these veins 
and masses both minerals occur in large grains. Very irregular- 
shaped masses of the calcite, also clearly secondary and often 
associated with pyrite are also found, especially in the crushed 
and broken portions of the rock. As before it occurs in large 
grains, frequently enclosing little bunches of a black, rod-like mineral. 
Little isolated crystals of calcite also occur in a similar manner. The 
calcite does not occupy cavities into which the other minerals have 
crystallized but seenis to have eaten its way into the feldspar, in some 
cases showing crystalline boundaries in the substance of the latter. 
Pyrite is present in considerable amount and is generally found well 
crystallized in little cubes. It occurs almost invariably in the crushed 
and broken portions of the rock and is very frequently associated with 
the calcite. In one slide, reproduced in Figure I, a mass of pyrite was 
observed enclosing a fragment of orthoclase, evidently a corner broken 
ofTfrom a large individual adjacent to it and with which its orientation 
was identical. In the figure the clear spaces show unbroken fragments 
of orthoclase separated by broken material, the result of crushing. A 
number of these small grains near the top of the cut, which are bound- 
ed by a somewhat heavier line, show one of the large fragments in the 
act of falling to pieces, a phenomenon which can be observed in most 
of the slides, when they are revolved between crossed Nicols. A num- 
ber of little cubes of 
pyrite are seen in the 
broken portion. After 
the corner of the large 
orthoclase individual 
had been broken off, 
the pyrite was evident- 
ly deposited in the 
crack and around the 
detached fra g m e n t. ■d'j 
The other little white tV^^J 
spaces in the same py- 
rite mass represent lit- 
tle inclosures of (juartz. 
These facts together 
with the occurrence of 
the pyrite almost ex- 
clusively in the crush- 
ed portions of the rock 
clearly prove the sec- 
ondary character of 
this mineral. 
As it was a point of much interest to ascertain if possible the man- 
ner in which the gold c>ccurred in the rock, the sections, twelve in 
number, representing five hand specimens very carefully examined 
FiGCRE I. 
^rranite showitiR cataclastic stnuture 
Magnitied 32 
•cciion oi till 
with depositiou of sucoiidary pvrite 
diameters. 
