Saponite

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Saponite
Saponite-432063.jpg
Nierig-grape-like mineral aggregate from creamy white saponite from the Großer Teichelberg , Bavaria (field of view 2.5 cm)
General and classification
other names

Soap stone

chemical formula
  • Mg 3 [(OH) 2 | Al 0.33 Si 3.67 O 10 ] • Na 0.33 (H 2 O) 4
  • Mg 3 [(OH) 2 | (Si, Al) 4 O 10 ] • (Ca, Na) x (H 2 O) y
  • (Ca 0.5 , Na) 0.3 (Mg, Fe 2+ ) 3 [(OH) 2 | (Si, Al) Si 3 O 10 ] · 4H 2 O
  • (Ca, Na) 0.3 (Mg, Fe) 3 (Si, Al) 4 O 10 (OH) 2 · 4H 2 O
Mineral class
(and possibly department) 		Silicates and germanates - layered silicates (phyllosilicates)
System no. to Strunz
and to Dana 		9.EC.45 ( 8th edition : VIII / H.20)
71.03.01b.02
Similar minerals Talc , pyrophyllite
Crystallographic Data
Crystal system monoclinic (pseudo-orthorhombic)
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group Cc (No. 9)Template: room group / 9
Lattice parameters a  = 5.30  Å ; b  = 9.21 Å; c  = 2 x 15.36 Å
β  = ≈ 97 °
Formula units Z  = 4
Physical Properties
Mohs hardness 1 to 2
Density (g / cm 3 ) 2.24 to 2.30
Cleavage completely after {001}
Break ; Tenacity moist plastic, dry brittle
colour white, yellow, gray, blue, green, reddish, brown
Line color White
transparency translucent to opaque
shine Greasy, earthy, matt
Crystal optics
Refractive indices n α  = 1.479 to 1.490
n β  = 1.510 to 1.525
n γ  = 1.511 to 1.527
Birefringence δ = 0.032 to 0.037
Optical character biaxial negative
Axis angle 2V = calculated: 20 to 26 °

The mineral saponite , also known as soapstone , is a rather seldom occurring sheet silicate with the chemical composition Mg 3 [(OH) 2 | Al 0.33 Si 3.67 O 10 ] · Na 0.33 (H 2 O) 4 and is therefore chemically water-containing Magnesium silicate with additional hydroxide ions .

Saponite crystallizes in the monoclinic crystal system and develops mostly fine-grained, bulbous or earthy to massive, but also leafy to fibrous mineral aggregates with a fat-like sheen on the surfaces. Saponite can only rarely be found in the form of tiny, tabular, pseudo-hexagonal crystals . In its pure form, saponite is theoretically colorless and transparent. Due to multiple light refraction due to lattice construction defects or polycrystalline training, it is practically always translucent to opaque white or takes on a gray, yellow, blue, green, reddish or brown color due to foreign admixtures . However, its line color is always white.

With a Mohs hardness of 1 to 2, saponite is one of the soft minerals that, like the reference mineral talc, can be scraped or scratched with the fingernail. According to its first description, Svanberg, the mineral, fresh from the mountain, is even so soft that it “can usually be spread like butter, which is why some miners, when they first encountered it, believed they had found a substance that could replace butter, to their amazement but soon learned that he was completely different from this. "

In the air, however, the mineral gradually hardens and finally disintegrates into a loose powder when it dries.

Etymology and history

A first, albeit imprecise, mention of the mineral is found in Axel Cronstedt's work, Attempt at a New Mineralogy , in 1758 when describing the various keys . As a subspecies of the "petrified" keys, it is described as dense and loose ( particulis impalpabilibus mollis ). Other names are Brianzoner Kreide , smectis and creta brianzonica . It is also known as the English Walkerthon and can be white ( Landsend in Cornwall), yellow, red and white (Landsend, Switzerland) and looks like Venetian soap.

Martin Heinrich Klaproth also reports on the English fulling earth , which is essential for the delicacy and quality of English cloth products. The fulling earth from Ryegate in the English county of Surrey is particularly valued among the cloth millers and its export is prohibited. In addition to the general description in terms of color, softness and the greasy feeling when touching the mineral, Klaproth especially emphasizes its characteristic property of quickly and silently disintegrating in water.

The name saponite from the Latin word sapo for 'soap', which is still valid today, was coined in 1830 by Lars Fredrik Svanberg (1805–1878) and is also an allusion to the soapy-greasy feeling when touching the mineral. Svanberg also gives a first complete description of the mineral including an approximate chemical formula.

The first location ( type locality ) for saponite is Lizard Point in Cornwall .

Type material , i.e. mineral samples from the first site ( type locality ), is stored at the Technical University Bergakademie Freiberg under catalog no. 44591 kept.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the saponite belonged to the mineral class of "silicates and germanates" and there to the department of "phyllosilicates", where it belongs together with hectorite , ferrosaponite , sauconite , spadaite , Stevensite and zinc silite formed the unnamed sub-group VIII / H.20 within the group of " clay minerals , more precisely the smectite - montmorillonite group".

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies saponite in the category of "phyllosilicates". This is, however, further subdivided according to the structure of the layers, so that the mineral, according to its composition, can be found in the sub-section "Layered silicates (phyllosilicates) with mica sheets , composed of tetrahedral and octahedral networks", where it is named after the "saponite group" with the System no. 9.EC.45 and the other members ferrosaponite, hectorite, sauconite, spadaite, stevensite, swinefordite and zinc silite .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the saponite to the class of "silicates and germanates" and there in the department of "layered silicate minerals". Here it is in the " smectite group (trioctahedral smectites) " with the system no. 71.03.01b can be found in the subsection “Layered Silicates: Layers of six-membered rings with 2: 1 clay minerals”.

Crystal structure

Saponite crystallizes monoclinically in the space group Cc (space group no. 9) with the lattice parameters a  = 5.30  Å ; b  = 9.21 Å; c  = 2 × 15.36 Å and β = ≈ 97 ° as well as 4 formula units per unit cell . Template: room group / 9

properties

Saponite breaks down very quickly in water. It also dissolves easily in warm hydrochloric acid , but it decomposes more slowly in cold sulfuric acid.

When moist (fresh from the mountain) the mineral is plastically deformable, but reacts brittle after drying.

Modifications and varieties

Of the compound Mg 3 [(OH) 2 | Al 0.33 Si 3.67 O 10 ] · Na 0.33 (H 2 O) 4 , only the monoclinically crystallizing modification saponite is known.

So far known varieties of saponite are

A pseudomorphism from saponite to olivite is known as bowlingite .

Medmontite , on the other hand, is not a copper-containing saponite (Cu saponite) as assumed, but a mixture of chrysocolla and various clay minerals.

Education and Locations

Clustered accumulation of dark green chamosite balls with light green saponite balls and copper crystals from the "Central Mine", Keweenaw County, Michigan, USA

Saponite forms hydrothermally in tunnels and geodes of volcanic rocks (mostly basalts ) or serpentinites . Accompanying minerals include calcite , celadonite , various chlorites , dolomite , epidote , solid copper , orthoclase and quartz .

As a rather rare mineral formation, saponite can sometimes be abundant at different sites, but overall it is not very common. A little more than 300 sites are known worldwide (as of 2017). In addition to its type locality Lizard Point in Cornwall (England), the mineral occurred in the United Kingdom (Great Britain) also in the places Coniston , Buxton and Cranmore ( Somerset ), also in England, and in County Antrim and Newcastle in Northern Ireland; Trotternish , Bowling ( Strathclyde ) and Barrhead in Scotland and Builth Wells in Wales.

Also worth mentioning due to the extraordinary saponite finds is Mont Saint-Hilaire in the Canadian Montérégie hills , where leafy saponite crystals up to one centimeter in diameter have been found.

In Germany saponite occurred among other things at Feldberg (Black Forest) in Baden-Württemberg; in several places in Franconia , Lower Bavaria and the Upper Palatinate in Bavaria; near Allendorf (Greifenstein) and Ortenberg in Hesse; near Sankt Andreasberg in Lower Saxony; in several places in the Eifel in Rhineland-Palatinate; near Walhausen (Saar) in Saarland and Schwarzenberg / Erzgeb. in Saxony.

In Austria, the mineral was previously at Waldenstein (Wolfsberg municipality) in Koralpe and at Sankt Paul in Lavanttal in Carinthia; found near Pingendorf (Drosendorf) in Lower Austria and near Klöch , Weitendorf and Leoben in Styria. In Switzerland, saponite has so far only occurred on Piz Mundin in the Samnaun group in the canton of Graubünden and at Ramsen SH in the canton of Schaffhausen.

Other sites are in Australia , Bolivia , Brazil , Chile , China , Curaçao , on the Ivory Coast , in France , Greece , India , Israel , Italy , Japan , Yemen , on the Kerguelen , Madagascar , New Caledonia , the Netherlands Antilles , Norway , Poland , Russia , Sweden , Slovakia , Spain , South Africa , South Korea , the Czech Republic , Hungary , the United States of America (USA) and Cyprus .

Saponite was also found in rock samples from the “Ninety East Ridge” from the Indian Ocean and outside of Earth on Mars .

High levels of saponite (greater than 50 percent by volume) have been found in drill core from the fault zone of California's San Andreas Trench . It is believed that the mineral there has an influence on the earthquake dynamics by reducing the friction between the continental plates.

use

Saponite occasionally as a natural cleanser some detergents added.

Synthetic saponites are used as a substitute for zeolites .

See also

literature

  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 754 (first edition: 1891).
  • Héliène Suquet, Henri Pezerat: Parameters influencing layer stacking types in Saponite and Vermiculite: A review . In: Clays and Clay Minerals . tape 35 , no. 5 , 1987, pp. 353-362 ( clays.org [PDF; 1.9 MB ; accessed on January 3, 2018]).
  • Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 311, 316 .
  • Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 1481, 1489-1490 .

Web links

Commons : Saponite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e f g h Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 (first edition: 1891).
  2. ^ Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  671 .
  3. ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  4. ^ IMA / CNMNC List of Mineral Names; September 2017 (PDF 1.67 MB)
  5. ↑ Webmineral - Saponite (English)
  6. ↑ a b c saponites . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 85  kB ; accessed on January 3, 2018]).
  7. ↑ a b c d e Mindat - Saponite (English)
  8. ↑ a b c d LF Svanberg: Saponite and Rosit, two new minerals . In: Annals of Physics and Chemistry . tape 133 , 1842, pp. 165–176 , doi : 10.1002 / andp.18421330912 ( limited preview in Google book search).
  9. ↑ Axel Cronstedt: Attempting a new mineralogy . Roth, Göttingen 1760, p. 68 ( limited preview in the Google book search - Swedish: Forsök til mineralogie, eller Mineral-Riketes Upställning . Stockholm 1758. Translated by G. Wiedeman).
  10. ^ Martin Heinrich Klaproth: Contributions to the chemical knowledge of mineral bodies . tape 4 . Rottmann, Berlin 1807, p. 334–338 ( available online at archive.org  - Internet Archive ).
  11. ^ Lars Fredrik Svanberg (chemist and university director) in the Swedish biographical dictionary. Retrieved January 3, 2018 (Swedish).
  12. ↑ Information on the type locality in the Mineralienatlas and Mindat
  13. ↑ Mineral Atlas: Saponite
  14. ↑ a b Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p.  578-579 .
  15. ↑ Mineral Atlas: Bowlingit
  16. ↑ Mindat - Number of localities for saponites
  17. ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Dörfler Natur ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 255 .
  18. ↑ a b List of sites for saponite in the Mineralienatlas and Mindat
  19. ^ Muted earthquakes , in FAZ from October 19, 2011, page N2
  20. ↑ Horst Rademacher: Dampened earthquakes , in: FAZ.net of October 24, 2011
  21. ↑ David A. Lockner, Carolyn Morrow, Diane Moore, Stephen Hickman: Low strength of deep San Andreas fault gouge from SAFOD core , Nature 472, pp. 82–85 (April 7, 2011)
  22. ↑ Patent DE69005189T2 (May 11, 1994): Synthetic saponite derivatives, a process for the production of these saponites and their use in catalytic (hydro) conversions