collier.] MINERALS ASSOCIATED WITH TIN ORE. 41 
Wolframite. — This is an ore of the metal tungsten, a tungstate of 
iron and manganese. It has a submetallic luster, a grayish or brownish- 
black color, and a black streak. Its specific gravity is 7.2 to 7.5, a 
little higher than that of cassiterite, but it is readily distinguished 
from the latter mineral by possessing a perfect cleavage. 
Epidote.— This complex silicate of calcium, aluminum, and iron is 
usually of a yellowish-green color. On Tin Creek it is found in 
prismatic crystals forming divergent groups resembling the tourma- 
line, which is also found there. In luster, streak, and hardness it 
resembles cassiterite, but its specific gravity is 3.25 to 3.50, only a 
little more than half as heavy as cassiterite. Before the blowpipe it 
fuses easily, and in the closed tube gives water. 
Magnetite and limonite. — These ores of iron are found in the placers 
associated with stream tin. They are often mistaken for tin ore, but 
are readily distinguished by the practiced eye. Magnetite can be dis- 
tinguished by the use of a magnet, while the red or brown streak of 
limonite serves to separate it from the tin ore. 
Fluor ite. — This mineral, commonly known as fluorspar, occurs in 
the bed rock associated with the tin ore wherever found in the York 
region. It is a simple chemical combination of fluorine and calcium, 
crystallizing in cubes and having a vitreous luster and usually a white, 
wine-yellow, greenish-blue, or violet-blue color. Its specific gravity 
is from 3.01 to 3.18. It is easily scratched with a knife, its hardness 
being about equal to that of calcite, from which it is distinguished by 
its cubic crystallization and failure to effervesce with hydrochloric 
acid. 
Quartz. — In varying amounts quartz is also associated in the bed 
rock with the tin ore. Usually it is readily distinguished from the 
cassiterite, but instances were common last summer where prospectors 
had mistaken a dark-colored, smoky quartz in small grains for cassit- 
erite. The specific gravity of quartz is 2.65 to 2.66, so that by the 
panning test the quartz can readily be separated. In powdered form 
smoky quartz and cassiterite resemble each other so much that the 
blowpipe test is often required to distinguish them. 
METHODS OF ASSAYING TIN ORE. 
Accurate assays of tin ore by ordinary methods are difficult on 
account of the readiness with which the tin combines with the various 
gangue minerals, forming silicates and stannites, which pass off with 
the slag. 
Nearly all writers on the subject of tin assays recommend that only 
rich ores, practically almost pure cassiterite, be treated by fire assay. 
Stream tin is ordinarily pure enough to give an approximately accurate 
result without further concentration, but lode ore, associated as it is 
