Properties of Orthoclase

Orthoclase is a common feldspar mineral, which is a group of rock-forming minerals that make up a significant portion of the Earth’s crust. Orthoclase specifically belongs to the potassium feldspar subgroup.

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Image of orthoclase mineral
Credit: Rob Lavinsky, iRocks.com - CC-BY-SA-3.0, via Wikimedia Commons

The following table provides a comprehensive list of orthoclase properties in both SI and US customary/Imperial units at normal temperature and pressure (NTP).

Note: click on the button to switch between Metric and Imperial units.

Table of Orthoclase Properties
Physical Properties
Metric
Chemical FormulaKAlSi3O8
Molar Mass278.33 g/mol
Crystal SystemMonoclinic
Mohs Hardness6
Density2500 - 2630 kg/m3
ColorWhite, pink, yellow, or red
DiaphaneityTransparent to translucent
LusterPearly, vitreous (glassy)
Cleavage(001) perfect, (010) good, (110) poor
FractureUneven
StreakWhite
Electrical PropertiesMetric
Relative Permittivity (εr)6.2

Note: unless stated otherwise, all values are taken at room temperature (approximately 20°C or 68°F) and 1 atm pressure. (1 atm = 101,325 Pa)

Related Pages
References: 1) Cardarelli, François. Materials Handbook: A Concise Desktop Reference. Switzerland: Springer International Publishing, 2018. 2) CRC Handbook of Chemistry and Physics, 97th Edition. United Kingdom: CRC Press, 2016-2017.