74 
GOLD. 
Case 1. Type specimens showing inodes of occurrence of 
gold in nature. These are — crystallized gold ; free gold in the vein- 
stuff; iron-pyrite containing gold disseminated through its sub- 
stance in invisible particles; gold in slate (the gold in the speci- 
men is invisible); combinedwith tellurium in sylvanite, petzite, etc., 
( telluride ores); sea sa?id containing minute grains of gold. A 
more extensive exhibit of placer gold may be found in Hall 32. 
Remainder of Case 1, Front. — Gold ores, California. 
These are chiefly quartz, or quartz and pyrite. They are dis- 
tinguished in general from ores of this class of other localities by a 
cleaner appearance, the absence of rust and disintegration, and by 
the smaller proportion of pyrite present. 
Cases 2, 3, Front. — Gold ores, Colorado. The ores of 
Cripple Creek, Col., which occupy the front of Case 2, should receive 
especial attention on account of their remarkable richness. Gold, 
which almost universally occurs free, is in these ores combined with 
tellurium (a substance related to sulphur) in the form of telluride 
ore . 
Case 3, Rear. — Gold ores, New Mexico and Arizona. The 
gold of New Mexico occurs chiefly associated with large quantities 
of silver and lead. The ores, worked chiefly for the latter 
metals, may be found in another part of the hall. The ores in this 
case are those in which gold is the principal metal sought. 
Case 4, Front.— Gold-silver ores, Colorado. Ores valuable 
both for silver and gold. The mixtures vary by imperceptible de- 
grees from the silver ores on one hand to the gold ores on the 
other. Gold and silver are very generally mingled to some degree 
in nature. 
Case 4, Rear. — Gold ores, British Columbia. 
Case 5. — Gold ores, Mexico and South America. Note the 
large quartz vein on the upper shelf as exhibiting the structure of 
the veins in which so many metalliferous deposits occur. 
The front of the case is occupied with ores from New Granada 
and Brazil; the rear, with ores from Ecuador and Mexico. The 
