REVIEWS 
Fifteenth Biennial Report, Colorado Bureau of Mines, for 1917 and 
1918. Denver: The State Printers, 1919. 
The mining is considered by counties and by products. The his- 
tory, recent development, production, and markets for the various ores 
are discussed. Non-metallic products are included; also a short note on 
oil shale possibilities. 
In general the report shows that the mining industry of the state is _ 
declining. Since 1915 the production of gold in the Cripple Creek dis- 
trict, the chief gold center of the state since 1893, has decreased from 
$13,683,494 to $8,300,000 (estimated) in 1918. The production of 
silver in Lake County (the leading silver-producing county) has fallen 
from 4,154,913 ounces in 1907 to 2,353,530 ounces (estimated) in 1918, 
although 1914 was a relatively good year. The production of lead has 
decreased less than that of the precious metals, but the decrease in both 
copper and zinc has been considerable in recent years. Lake County 
produces more silver, lead, copper, and zinc than any other. In 1916 
the state produced nearly $5,000,000 worth of tungsten, but the esti- 
mate for 1918 is less than half this figure, due to decreased demand and 
possibly to the irregularity of the veins. 
Colorado leads the world in the production of molybdenum, the 
main deposit (said to be the largest known) being in the western part 
of Summit County. In 1918 the state had an estimated production of 
94,000 pounds of uranium, the largest except in 1914. Two million 
pounds of vanadium (largest production to date) is the estimate for 
1918. 
The total mineral.production of the state to 1917 is as follows: 
Gola eh ihc Mente oan nurs $623;047,100)) |. 54 tues 6 ee 
Silver wactle LAr nee en 466,463,217 593,790,442 fine ounces 
Lead sy Dah Ms aie Trea ae 173,909,020 3,962,140,896 pounds 
Copper v2.2) ene ae een 355755,139 237,422,282 pounds 
VAX CMMI ARENA aM CREO US ete 106,310,030 1,484,929,849 pounds 
$1,405,484,565 
| Dane 
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