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Hectorite Hydrous magnesium iron silicate Hector, California.jpg
Hectorite from California
(repeating unit)
(empirical: Na3(Mg,Li)30Si40O100(OH)20)
Strunz classification9.EC.45
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 5.25 Å, b = 9.18 Å
c = 16 Å; β = 99°; Z = 2
ColorWhite, cream, pale brown, mottled
Crystal habitThin laths and aggregates
Cleavage[001] Perfect
Mohs scale hardness1 - 2
LusterEarthy to waxy
DiaphaneityTranslucent to opaque
Specific gravity2-3
Optical propertiesBiaxial (-) - 2V small
Refractive indexnα = 1.490 nβ = 1.500 nγ = 1.520
Birefringenceδ = 0.030

Hectorite is a rare soft, greasy, white clay mineral with a chemical formula of Na0.3(Mg,Li)3Si4O10(OH)2.[1]

Hectorite was first described in 1941 and named for an occurrence in the United States near Hector (in San Bernardino County, California,[3] 30 miles east of Barstow.) Hectorite occurs with bentonite as an alteration product of clinoptilolite from volcanic ash and tuff with a high glass content.[1] Hectorite is also found in the beige/brown clay ghassoul, mined in the Atlas Mountains in Morocco.[4]

Despite its rarity, it is economically viable as the Hector mine sits over a large deposit of the mineral. Hectorite is mostly used in making cosmetics, but has uses in chemical and other industrial applications, and is a mineral source for refined lithium metal.[5]


  1. ^ a b c Handbook of Mineralogy
  2. ^ Hectorite data on Webmineral
  3. ^ a b Ralph, Jololyn and Ida (2007): Hectorite on Mindat.org
  4. ^ Benhammou,, Abdelaziz;; Tanouti,, Boumediene;; Nibou, Lahbib;; Yaacoubi, Abdelrani;; Bonnet, Jean-Pierre (2009). "Mineralogical and Physicochemical Investigation of Mg-Smectite from Jbel Ghassoul, Morocco". Clays and Clay Minerals. 57 (2): 264–270. Bibcode:2009CCM....57..264B. doi:10.1346/CCMN.2009.0570212.
  5. ^ Moores, Simon (2007) Between a rock and a salt lake; Industrial Minerals, June '07