Properties of Montmorillonite

Montmorillonite is a type of clay mineral belonging to the smectite group. It is named after the Montmorillon region in France where it was first discovered.

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

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

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

Table of Montmorillonite Properties
Physical Properties
Metric
Chemical FormulaNa0.2Ca0.1Al2[Si4O10](OH)2·10H2O
Crystal SystemMonoclinic
Mohs Hardness1 - 2
Density2290 - 2360 kg/m3
ColorPale yellow to olive green
DiaphaneityTranslucent
LusterWaxy to resinous
Cleavage(001) perfect
FractureConchoidal to fibrous

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.