Saponite

Saponite is a trioctahedral mineral of the smectite group. Its chemical formula is Ca_0.25(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.

Saponite
Saponite (light green) mixed with chamosite (dark green) and copper
General
Category	Phyllosilicates Smectite group
Formula (repeating unit)	Ca0.25(Mg,Fe)3((Si,Al)4O10)(OH)2·n(H2O)
Strunz classification	9.EC.45
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/m
Unit cell	a = 5.3 Å, b = 9.14 Å c = 16.9 Å; β = 97°; Z = 2
Identification
Color	White, yellow, red, green, blue
Crystal habit	Granular - Massive
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]

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.

Occurrence

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] Europe's largest primary diamond deposit, Lomonosov, in the Primorsky District of Arkhangelsk Oblast is an area of intensive accumulation and storage of saponite at the tailings.

Saponite tailings storage facilities eastwards of the open-pit mines at the Arkhangelskaya and Karpinskogo-1 pipes, Russia [5]

Application

The forecasted mass of saponite to be discharged into the tailings of diamond ore processing makes up millions of tons. Worryingly, when macro- and micro-components are found in non-hazardous concentrations, fewer efforts are put into the environmental management of the tailings, though technogenic sediments offer prospects for reuse and valorization beyond their traditional disposal. Saponite is a demonstrative example of the tailings constituent that is often left unfairly mistreated.

Electrochemical separation helps to obtain modified saponite-containing products with high smectite-group minerals concentrations, lower mineral particles size, more compact structure, and greater surface area. These characteristics open possibilities for the manufacture of high-quality ceramics and heavy-metal sorbents from saponite-containing products.[6] Furthermore, tail grinding occurs during the preparation of the raw material for ceramics; this waste reprocessing is of high importance for the use of clay pulp as a neutralizing agent, as fine particles are required for the reaction. Experiments on the Histosol deacidification with the alkaline clay slurry demonstrated that neutralization with the average pH level of 7.1 is reached at 30% of the pulp added and an experimental site with perennial grasses proved the efficacy of the technique. Moreover, the reclamation of disturbed lands is an integral part of the social and environmental responsibility of the mining company and this scenario addresses the community necessities at both local and regional levels.[5]

See also

• Classification of minerals
• Hectorite – Rare trioctahedral (Mg²⁺, Li⁺) sodium smectite, phyllosilicate mineral
• Nontronite – Dioctahedral (Fe³⁺) smectite, phyllosilicate mineral
• List of minerals

References

1. Webmineral data
2. Mindat.org
3. 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. Bibcode:1993GeCoA..57.3123Z. doi:10.1016/0016-7037(93)90298-B.
5. Pashkevich, M.A.; Alekseenko, A.V. (2020). "Reutilization Prospects of Diamond Clay Tailings at the Lomonosov Mine, Northwestern Russia". Minerals. 10 (6): 517. doi:10.3390/min10060517. This article incorporates text available under the CC BY 4.0 license.
6. Chanturiya, V.A.; Minenko, V.G.; Makarov, D.V. (2018). "Advanced Techniques of Saponite Recovery from Diamond Processing Plant Water and Areas of Saponite Application". Minerals. 8 (12): 549. doi:10.3390/min8120549. This article incorporates text available under the CC BY 4.0 license.

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