



Arnold O. Tanner, mineral commodity specialist for the U.S. Geological Survey, compiled the following information on feldspar, one of the most abundant and widespread rock-forming mineral groups on Earth.
Feldspar is the general name of members of a group of closely related anhydrous minerals distinguished by the presence of aluminum and silica in combination with varying proportions of one or more base elements, including potassium, sodium and calcium. The particular mineral is named after its major base element: potassium feldspar, sodium feldspar or calcium feldspar. Feldspars are major components of most igneous rocks and constitute a large part of at least the outer layers of Earth and the moon. By some estimates, feldspar constitutes 60 percent of Earth’s crust.
Feldspar, usually of the potassium or sodium type or mixtures of the two, is principally used in the manufacture of glass and ceramics. In both applications it acts as a flux. Feldspar’s alkali content lowers the melting temperature of the mixture, prompting faster melting and fuel savings. Fluxes melt in early stages of the ceramic firing process, forming a glassy matrix that bonds the other components of the system together. In glassmaking, the mineral’s alumina content enhances the workability of the product and improves product hardness, durability, thermal endurance and resistance to chemical corrosion. Feldspar also serves as a binder and filler in paints and in various abrasive applications. In 2010 in the U.S., some 70 percent of feldspar was used for glass.
Feldspar mining in North America may have begun in pre-Colonial times. Examination of shards from a large number of prehistoric culture centers, widely distributed in both place and time, shows that native potters often depended on feldspar from feldspathic sands to provide the temper (increased hardening) for their clay pots. A small quantity of the mineral, reputedly obtained from Native Americans, is said to have been shipped to Europe in 1744 from somewhere in the mountainous part of what is now North Carolina, the same area that two centuries later would become the primary focus of the U.S. feldspar industry.
Economic resources of feldspar greatly increased in 1940 with the development of successful froth flotation methods for the separation of feldspar. Prior to this, the industry was dependent on more costly hand-cobbing procedures, generally with a handheld hammer, involving the separation of feldspar from worthless or otherwise undesirable minerals.
For more information on feldspar and other mineral resources, visit http://minerals.usgs.gov/minerals/.
U.S. Oil & Petroleum Imports (millions of barrels per day)
Oil and petroleum imports data are preliminary numbers taken from the American Petroleum Institute’s Monthly Statistical Report. For more information visit www.api.org.
Feldspar production and consumption:
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