What is it?
Kyanite is a typically blue silicate mineral, commonly found in aluminium rich metamorphic or sedimentary Rocks.
Kyanite is a member of the alumino-silicate series, which includes the polymorphs, alusite and sillimanite, which have the same chemical composition (Al2O3.SiO2) as alusite and sillimanite but it is distinguished from those two minerals by its physical properties.
Properties:Kyanite is easily distinguished from sillimanite and alusite by its tabular, long bladed, circular form and by bluish color; and slightly lower hardness than sillimanite and alusite. Another important property is its double hardness. Its specific gravity is 3 to 3.7.
- Tactile properties: It is smooth, slippery and soapy.
- Visual properties:
- Color: It is blue, green and white in color.
- Lustre: It is vitreous
- Streak: It is white.
- Diaphaneity: It is transparent to translucent.
- Structural properties:
- Hardness: 4-7 mohs (4.5 when scratched parallel to the long axis of the crystal and approximately 6.5 when scratched perpendicular to or across the long axis)
- Specific gravity: 3.6
- Affinity to water: It is hydrophobic and insoluble in water.
- Heat properties:
- It does not conduct heat.
- Its notable volume increase with heat.
- It has high specific heat capacity.
- It can withstand temperatures upto 1300ºC.
- Electric properties: It does not conduct electricity.
- Combustion properties: It is non explosive and non-inflammable.
- Chemical properties: It is insoluble in acids and alkalis.