92 Microscopical Character of the Ore. — Adams- 
by reflected light. In ten of them no trace of gold could be detected, 
but in the other two both from the same hand specimen, a few little 
bright yellow spots having exactly the color of gold could be distinctly 
seen in three ofthepyrite grains. These spots were quite diflferent 
in color from the pyrite and easily distinguished from it. Figures 
2 and 3 represent two of these grains of pyrite with their inclusions of 
gold. In order to make certain of 
the character of the yellow spots, 
the cover was removed from one 
of the sections and a portion of the 
section containing the grain of py- 
rite seen in figure 3 was removed to a 
clean glass slide and treated with 
hot concentrated nitric acid. The 
acid was found to dissolve away 
the pyrite with effervesence leav- 
ing the bright yellow spangles of 
gold behind. The gold therefore 
, , 1 , . . Grain of pyrite liolding inclusions of 
occurs m part at least, in a free native gold, magnified 4.3 diameters. 
State and imbedded in the pyrite ; no gold could be detected except in the 
pyrite. The zeolite mentioned as occurring in the rock is present in 
small amounts and is not seen in^every section. It is evidently second- 
ary, occuring in small irregular-shaped masses as amicrocrystalline ag- 
/ s. gregate. The individual grains were too small to 
/ / allow its optical character to be determined. The 
/ / cover was however removed from one section 
^,,Ji^ ^^ containing it and the rock was treated with con- 
centrated hydrochloric acid in the cold for half an 
hour. On treating with fuchsine the aggregate 
was found to take up the coloring matter readily, 
showing that it had been decomposed by the acid 
J and is probably one of the zeolites. 
It is a matter of difficulty to determine wheth- 
FIGURE o. 
Grain of pyrite with er any cases of secondary enlargement are to be 
gold^*'°^ ° na i\e Jq^j-^^j Jj-, ^j^g sections. I believe however that in 
some cases the broken fragments have commenced to grow again by 
secondary deposition of material around their edges, although on ac- 
count of the ragged character of the latter due to breaking away of 
fragments by crashing, it is very difficult in some cases to determine 
whether an irregular boundary is the result of crushing or of a second- 
ary growth. The outline of some grains is very similar to that of a 
feldspar crystal showing secondary enlargement which is figured 
(Fig. 1, b.) in the preliminary notice of a paper on the Archean Geol- 
ogy of Missouri by Erasmus Haworth, (John Hopkins University 
Circulars, No. 65, April 1888). The feldspar of the rock is generally 
much clearer and more transparent along the borders of the veins and 
irregular masses of secondary quartz. In one case an individual of de- 
composed plagioclase was observed which was very clear and fresh 
