Properties of Borax

Borax, also known as sodium tetraborate, or disodium tetraborate, is a naturally occurring mineral compound with the chemical formula Na2B4O7·10H2O. It consists of soft, colorless crystals that dissolve easily in water.

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Image of borax mineral
Credit: Marie-Lan Taÿ Pamart, CC BY 4.0, via Wikimedia Commons

The following table provides a comprehensive list of borax 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 Borax Properties
Physical Properties
Metric
Chemical FormulaNa2B4O7·10H2O
Molar Mass381.368 g/mol
Crystal SystemMonoclinic
Mohs Hardness2 - 2.5
Density1730 - 1900 kg/m3
ColorColorless, white, gray, or greenish white
DiaphaneityTranslucent to opaque
LusterResinous, greasy
Cleavage(100) perfect, (110) perfect
FractureConchoidal, brittle
StreakWhite
Thermal PropertiesMetric
Melting Point743 °C

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.