Of such minerals as quartz, grindstone, millstone, emery stone, mineral paints, talc and salt, there seems to be enough to meet the needs of the future as well as the present. Such supplies as sulphur, asphalt, magnesia, borax, and asbestos, as well as coal and iron, are not very plentiful. If used carelessly, they will be exhausted in a few years; if wisely, they may be expected to last beyond the limits of the present century.
Our supplies of quicksilver, antimony, graphite, mica, tin, nickel, platinum, and many minerals less well known, as well as our petroleum, natural gas, copper, gold, silver, lead, zinc, and phosphate rock will be almost exhausted well within the present century unless large new deposits are discovered.
REFERENCES
Report of National Conservation Commission.
The Conservation of Mineral Resources. U. S. Government Reports.
Report of the U. S. Geological Survey.
Production of Gold in 1908. U. S. Government Reports.
Production of Silver in 1908.
Production of Lead in 1908.
Production of Zinc in 1908.