MICHIGAN ACADEMY OF SCIENCE. 
55 
quartz forms streaks running through the coarse grained. In some 
cases, two coarse grains are separated by a row of fine grains, which 
have apparently been derived from the former by crushing. In one 
specimen an area, 1.0 mm. in diameter, of fine grained quartz encloses 
an isolated coarse grain 0.2x0.4 mm. in diameter. The finely crystalline 
has apparently been formed largely by granulation of the larger grains. 
The small particles are firmly cemented together and there was evi- 
dently some solution and recrystallization though the cement is not 
distinguishable under the microscope. 
In the fine grained portions there is a notable absence of large fluid 
inclusions and evidently some such fluid was able to move among the 
fine quartz particles. The presence of fluid inclusions in the quartz in- 
dicates that it was not when solidifying. The granulation of the quartz 
indicates that it was comparatively cold when crushed. 
MODES OF OCCURRENCE OF GOLD IN DOME MINE QUARTZ. 
1. Gold completely enclosed in one grain of coarsely crystalline 
quartz, e.g. One grain of quartzi 0. 5x0.8 mm. in the plane of the sec- 
tion completely encloses three isolated grains of gold. The small size 
of these gold grains makes it appear unlikely that they were not com- 
pletely enveloped in the quartz, though there is a possibility that they 
were not. Another quartz grain 1.0 mm. in diameter enclosed three 
ragged grains of gold about 0.01 mm. in diameter and several gold par- 
ticles 0.01 mm. or less in diameter. 
2. Gold in spaces between grains of coarsely crystalline quartz, e.g. 
One U shaped area of gold 2 mm. long and 0.02 to 0.06 mm. wide forms 
a ragged band between coarse quartz grains. It forms a border for 
two-thirds the periphery of one quartz grain — hence the shape. In sev- 
eral sections, there is gold showing similar relation to coarse quartz 
grains. 
3. Gold in crystals and grains of pyrite, e.g. One area of pyrite 0.5 
mm.xl.O mm. encloses several irregular patches of gold, most of which 
are less than 0.1 mm. in diameter. Four of these gold grains are com- 
pletely within the pyrite, while a much greater number are partially 
enclosed by the pyrite and partially by quartz. A second and rectangular 
area of pyrite 0.5 mm.xO.l mm. has along its middle portion five areas 
of gold. The string of gold particles continues from either end of the 
pyrite into clear quartz. Another specimen shows an area of gold 0. 6x0.1 
mm. which is four-fifths enclosed by pyrite, while the end projects into 
colorless minerals. The part of the gold not enclosed by pyrite is on 
one side in contact with calcite and on the other with a grain of quartz. 
4. Gold grains in calcite, completely or partially enclosed. A 
twinned individual of calcite 1 mm.x0.5 mm. is enclosed chiefly by fine 
grained quartz, and one end is in contact with an area of pyrite 1 mm. in 
diameter. Around the edge of the calcite and in immediate contact 
with it, are nine distinct particles of gold. Within the calcite and ar- 
ranged in a string roughly following a cleavage direction, are six grains 
of gold 0.02 to 0.03 mm. in diameter. 
A second specimen shows an area of calcite 0.1 mm. x 1.0 mm., enclos- 
ing a number of small gold grains. This calcite is partially enclosed in 
fine quartz, but it also fills a fracture in one large quartz grain. This 
same specimen shows gold in quartz with no calcite in contact. 
