What is it?
Feldspar comprises of group of aluminum silicate that contains sodium (NaAlSi3O8), potassium (KAlSi3O8)or calcium(CaAl2Si2O8).Feldspars are the most abundant mineral in Earth’s crust, making up more than 60% of the crust.
The basic unit of feldspar structure is a tetrahedron of silicon and oxygen (SiO4) and aluminium and oxygen (AlO4–). These tetrahedra are covalently bonded to each other through oxygen atoms to form a three dimensional framework. Low-charge cations like Na+, K+ or Ca2+ occupy the larger voids in the tetrahedral framework to provide charge balance against the aluminium tetrahedra.
- Tactile properties: It is rough and abrasive.
- Visual properties:
- Color: Orthoclase: It is light colored; usually white, pink, yellow, or cream in color. Microcline: It is white, pink, pale yellow, or sometimes green-blue in color. Plagioclase: Gray to grayish-white color is common, but may also be white, pink or pale yellow in color.
- Lustre: It is vitreous.
- Streak: It is white.
- Diaphaneity: It is opaque.
- Structural properties:
- Hardness: 6-6.5 mohs.
- Specific gravity:2.6
- Affinity to water: It dissolved slightly in water, releasing the alkali metal ions.
- Affinity to oil: It has low oil absorption capacity.
- Heat properties:
- Thermal conductivity: 2.3-2.5 W/m/K.
- Specific heat capacity: 222 J/M/K.
- Coefficient of expansion: 13.1 to 30.6.
- Melting point: 1200 to 1400 °C.
- Decomposition temperature: 1473K
- Electric properties: It does not conduct electricity.
- Combustion properties: It is non explosive and non inflammable.
- Chemical properties: It dissolves in acid, releasing the alkali metal ion and aluminium ion