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

Moh's 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.