Feldspar
Feldspar is the name given to a group of minerals distinguished by the presence of alumina and silica (SiO2) in their chemistry. This group includes aluminum silicates of soda, potassium, or lime. It is the single most abundant mineral group on Earth. They account for an estimated 60% of exposed rocks, as well as soils, clays, and other unconsolidated sediments, and are principal components in rock classification schemes. The minerals included in this group are the orthoclase, microcline and plagioclase feldspars.
Type
Mineral
Mineral Classification
Silicate
Chemical Formula
KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8
Streak
White
Mohs Hardness
6-6.5
Crystal System
triclinic, monoclinic
Color
pink, white, gray, brown
Luster
Vitreous
Fracture
conchoidal, uneven
Description
Feldspar is the name given to a group of minerals distinguished by the presence of alumina and silica (SiO2) in their chemistry. This group includes aluminum silicates of soda, potassium, or lime. It is the single most abundant mineral group on Earth. They account for an estimated 60% of exposed rocks, as well as soils, clays, and other unconsolidated sediments, and are principal components in rock classification schemes. The minerals included in this group are the orthoclase, microcline and plagioclase feldspars.
Relation to Mining
The top states producing feldspar are North Carolina, Virginia, California, Oklahoma, Idaho, Georgia and South Dakota, in descending order of estimated tonnage. Feldspar processors reported co-product recovery of mica and silica sand.
Feldspar is mined from large granite bodies (called plutons by geologists), from pegmatites (formed when the last fluid stages of a crystallizing granite becomes concentrated in small liquid and vapor-rich pockets that allow the growth of extremely large crystals), and from sands composed mostly of feldspar.
Because feldspar is such a large component of the Earth’s crust, it is assumed that the supply of feldspar is more than adequate to meet demand for a very long time to come. Present mines worldwide are adequately meeting the need for raw feldspar.
Hard-rock mining for feldspars is done by open-pit methods, either by the mine owner or by contractors. After the feldspar ore is drilled and blasted, secondary breakage is performed with a conventional drop ball. Ore is then loaded with a hydraulic shovel onto trucks and hauled to the crushing plant, which is adjacent to the flotation plant.
Uses: Feldspar is used to make dinnerware and bathroom and building tiles. In ceramics and glass production, feldspar is used as a flux. A flux is a material that lowers the melting temperature of another material, in this case, glass.
Substitutes and Alternative Sources
Feldspar can be replaced by other minerals and mineral mixtures of similar physical properties. Minerals that could be used to replace feldspar include pyrophyllite, clays, talc, and feldspar-silica (quartz) mixtures. The abundance of feldspar will make these substitutions unnecessary for the foreseeable future.
Uses
Feldspar is used to make dinnerware and bathroom and building tiles. In ceramics and glass production, feldspar is used as a flux. A flux is a material that lowers the melting temperature of another material, in this case, glass.
Substitutes and Alternative Sources
Feldspar can be replaced by other minerals and mineral mixtures of similar physical properties. Minerals that could be used to replace feldspar include pyrophyllite, clays, talc, and feldspar-silica (quartz) mixtures. The abundance of feldspar will make these substitutions unnecessary for the foreseeable future.
