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Title: Saponite  
Author: World Heritage Encyclopedia
Language: English
Subject: Illite, Chlorite group, Dickite, Kaolinite, Kerolite
Collection: Aluminium Minerals, Calcium Minerals, Clay Minerals Group, Iron Minerals, Magnesium Minerals, Smectite Group
Publisher: World Heritage Encyclopedia


Saponite (light green) mixed with chamosite (dark green) and copper
Category Phyllosilicates
Smectite group
(repeating unit)
Strunz classification 9.EC.45
Crystal symmetry Monoclinic prismatic
H-M symbol: (2/m)
Space group: C 2/m
Unit cell a = 5.3 Å, b = 9.14 Å, c = 16.9 Å; β = 97°; Z = 2
Color White, yellow, red, green, blue
Crystal habit Granular - Massive
Crystal system Monoclinic
Cleavage {001} perfect
Tenacity Brittle dry, plastic when hydrated
Mohs scale hardness 1.5
Luster Greasy, dull
Streak White
Diaphaneity Translucent
Specific gravity 2.24 - 2.30
Optical properties Biaxial (-)
Refractive index nα = 1.479 - 1.490 nβ = 1.510 - 1.525 nγ = 1.511 - 1.527
Birefringence δ = 0.032 - 0.037
Pleochroism X = colorless, light yellow to green-brown; Y = Z = colorless, greenish brown to dark brown
2V angle Calculated: 20° to 26°
References [1][2][3]

Saponite is a trioctahedral mineral of the smectite group. Its chemical formula is Ca0.25(Mg,Fe)3((Si,Al)4O10)(OH)2·n(H2O).[2] It is soluble in sulfuric acid. It was first described in 1840 by Svanberg. Varieties of saponite are griffithite, bowlingite and sobotkite.

It is soft, massive, and plastic, and exists in veins and cavities in serpentinite and basalt. The name is derived from the Greek sapo, soap. Other names include bowlingite; mountain soap; piotine; soapstone.


Saponite was first described in 1840 for an occurrence in Lizard Point, Landewednack, Cornwall, England.[2] It occurs in hydrothermal veins, in basalt vesicles, skarns, amphibolite and serpentinite. Associated minerals include celadonite, chlorite, native copper, epidote, orthoclase, dolomite, calcite and quartz.[3]

Saponite is found in Ząbkowice Śląskie in Silesia, Svärdsjö in Dalarna, Sweden and in Cornwall, UK. The soap stone of Cornwall is used in the porcelain factory. Saponite is also found in the "dark rims" of chondrules in carbonaceous chondrites and seen as a sign of aqueous alteration.[4]

See also


  1. ^ Webmineral data
  2. ^ a b c
  3. ^ a b Handbook of Mineralogy
  4. ^ Zolensky, Michael; Barrett, Ruth; Browning, Lauren (July 1993). "Mineralogy and composition of matrix and chondrule rims in carbonaceous chondrites". Geochimica et Cosmochimica Acta 57 (13): 3123–3148.  

This article contains material from the U.S. Bureau of Mines Dictionary of Mining, Mineral, and Related Terms.

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