Soapstone

Soapstone, rough stones in different colors

Soapstone ( steatite , Lavezstein , Talcusstein , soapstone , ital. Pietra ollare ; double. Pierre ollaire ; Engl. Soapstone ) is a naturally occurring, massive or slaty occurring chemical substance , depending to the composition as a mineral or rock applies. Its main ingredient is talc ; it turns soapstone into a mineral in its pure form. In many deposits, accompanying minerals are added and thus have a coloring and structure-defining effect. In this case one speaks of a rock. Frequently occurring secondary components are magnesite , serpentine and various chlorites . There are transitional forms to talc slate, talc rock, green slate and chlorite slate .

Due to its low hardness ( Mohs hardness  = 1) and thus easy workability, soapstone was already a popular natural and stone stone in the ancient Orient , Egypt , China and Scandinavia , which was mainly processed into seals , sculptures and various household items such as containers and cookware .

properties

Pure white soapstone sculpture ( The Thinker by Ruth Kopp )

Sculpture made from six different types of soapstone ( species protection by Arnold Schoger )

composition

Pure soapstone consists of up to 100% talc (mineral) and is easy to scratch with a fingernail. However, many types of soapstone contain only around 40 to 50% talc and some other mineral additions such as magnesite (40 to 50%) and pennine (5 to 8%, clinochlor variety in Finnish soapstone). These are then difficult or impossible to scratch with the fingernail.

Physical Properties

• Mohs hardness : 1 (100% talc)
• Density : 2.75 g / cm³
• Thermal conductivity : λ = 3.3 W / (K m) (at 20 ° C)
• Specific electrical resistance : ρ = 10 ¹¹ Ω · m² / m (at 20 ° C); ρ = 10 ³ to 10 ⁵ Ω m² / m (at 600 ° C)
• Specific heat capacity : c = 0.98 kJ / (kg Δϑ) or 0.98 J / (g Δϑ)

Colours

The most common colors are white, purple, pink, green, gray, black, brown and blue, but these occur in many shades and cannot always be clearly assigned to a color. There are also multi-colored marbled varieties that sometimes have harder inclusions and are therefore not always suitable for mechanical or manual processing.

Multi-colored marbled varieties are often ferromagnetic , whereby significant differences in intensity can occur within a stone. Particularly harder inclusions show a clear magnetism, which can also influence a compass needle.

etymology

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General

Soapstone got its name because of its properties of being greasy to the touch and showing a grease-like or bacon- like sheen on its surfaces . The interpretations on the basis of some foreign-language names and the form Lavez or Lavetzstein or Lavezzstein , which is common in southern Switzerland, are complex. A medieval name for this stone was Talcus .

In terms of landscape (especially in Switzerland and Valtellina ), the name Lavezstein is common, for the older Italian lavezzo or laveggio 'pot'.

The western and southern Alps are a traditional mining area for soapstone. An important center was the Val Lavizzara in northern Ticino . The term lava stone, which only occurs regionally today, is associated with the name of the valley or this landscape. A family name Lavizzari is recorded in this valley. In this context it is narrated: “… and in this chain of rocks are the mountains di Lavezzi, which are named because the Lavezzstein or pot stone is dug into them.” (1760) and “… The Lavizzara valley… It takes its name from the Lavezzi or ports and kitchen utensils turned from certain stones. "(1766)

In Latin, the word lavātiō ( -ōnis ) stands for washing, bathing, bath and bath water and lăvō for the verbs bathe and wash. Today in Switzerland (including German Swiss, dial. And hochsprachl.) For sinks , the term sink (fr. Le lavabo , dt. The sink ) is used. In Italian, lavare stands for to wash, and lavello for sink / wash basin and the term lavatore for the person who is the washer . The Latin words lǎbrǔm and lǎvābrǔm mean basin, tub, bathtub. The Roman kettle is called labra . By shifting the sound, “b” became “v”.

However, some etymological dictionaries bring the concept Lavetz with soapstone in connection, without giving a coherent and scientifically safe occupied derivation from the language research.

Among other things, there is the literary note “There are also 'clays', which were previously called 'fullers' because they were used for fulling (degreasing) wool."

Regional

Contemporary explanations of the meaning of the word can be seen from old documentary sources, for example for Laffetsch (Schlandersberg 1401) for "large kettle for cooking and washing" and lafetz for "large kettle for cooking, washing". This shows the ambiguity of this term in the temporal context when the stone found intensive processing and demand.

In the 13th century, the name lavezzo was also applied to metal kettles made of bronze and copper. Secondary one finds Laveggio in Italian for Cauldron, although primarily for paiuolo and saucepan pentola stand.

Modern language research in the southern Alpine region further differentiates the term. The first textual evidence comes from the 13th century from the Veneto region and from the beginning of the 14th century from a Tuscan source. Traveling craftsmen (tinkerers, chimney sweeps, bricklayers, crockery dealers, etc.) spread the term lava stone (Lafetsch stone) from the regions where it was extracted in Valtellina and Ticino. The origins of the Middle High German Lafetsch forms and their adequate Central Alladin words are assigned to the regions of Lombardy and Ticino in linguistic research . This coincides with important deposits of soapstone in some Alpine valleys. Materials and objects were often referred to in terms of their application and processing. This gives those groups a certain degree of definition sovereignty that has the greatest possible overview of their material or its processing and areas of application.

A look at liturgical practice helps to broaden the perspective on the complex naming problem. Vessels and instruments that are used by the Roman Catholic Church to wash hands during worship are referred to as lavabo . Soapstone can also be identified as a material for baptismal fonts and holy water basins (e.g. the holy water basin in the Church of Madonna della Rovana in Cevio / 17th century / material from Val Peccia ).

These ablutions had a symbolic and practical hygienic background. The symbolic meaning has been celebrated from Psalm 25 (6-12) since Franconian times: Lavabo inter innocentes manus meas… / In innocence I want to wash my hands…. "The initial word was named for the vessels and devices."

Due to its versatile use, lava stone / soapstone is the material that people have become indispensable for their daily work-intensive activities. As “washing powder”, water vessel, plate and pot, it was equally the material for everyday use such as baptismal font and holy water vessel in people's religious life. The sense of connection Lavetzstein results from the fact that from the very soft soapstone not only cooking pots (lat. Olla , pot '/ French. Pierre d'ollaire , soapstone'), but originally sink and were -tröge made. This saucepan production reached its peak in the Middle Ages.

According to the latest findings, the term lavec is to be seen as a wandering word that was spread by wandering craftsmen from Lombardy in the southern Alps. The final etymological explanation, if at all possible, is reserved for further arduous and interdisciplinary research.

Older sources cite soapstone with typical contemporary uses:

• “The pot stone - cutting stone, soft stone, gilt stone, lava stone - translucent at the edges, is a greenish-gray, indistinctly granular talc or an intimate mixture of talc, chlorite, mica, magnetic iron and the like. ... The lava stone (from Lavezzo: a pan, a kettle) is still fresh and moist to work with than serpentine, even lighter than dry clay. "" At Plürs in Graubündten, it was used for all kinds of vessels, especially cooking utensils (hence caldarium ), processed. From Como, where he was brought to market, Pliny called him: lapis comensis . "

• “The property of several mineral substances of earthy or dense composition to eagerly suck in fatty oils makes them suitable to extract contaminating greases from silk, woolen and other witnesses; they are therefore used for fulling them and for making grease stains. These minerals are: Fuller's earth, clay, cimolite, mountain soap, soapstone, ... "" Fuller's earth ... feels very greasy and easily dissolves in water into a fine, mild, soapy sludge. "" Fuller's earth is, ... in some areas for cleaning of linen and used in many cases where soap is usually used. "

Soapstone deposits in the southern Alps have the property that, in addition to the solid pieces of rock, there is a lot of loose material that cannot be used for turning objects. The large amounts of soapstone powder produced by turning and other machining techniques would normally be waste, but they were used like the loose waste from soapstone mining to make soap powder.

Ancient uses and terms

For the etymological derivation, the explanations on ancient uses must also be observed. Various materials were used for this, but rock is very often documented in the literature and among the finds. The basins were used as agricultural implements in the production of oil and wine, and they were also used in the house as storage containers for liquids and food. In addition, labrum denotes the wash basin within the Roman baths (Vitruv V 10.4), many of which have been preserved. These are mostly very flat, round basins with a relatively large diameter. They were often pierced in the middle so that the water could flow into the basin under pressure like a fountain. The origin of these basins lies in the basins of the Greek baths, the foot baths ( οί ποδανιπτηρες ) on the one hand and the actual wash basins ( τα λουτηρια ) on the other. Stone louteria are often found in temples, the basins are sometimes so flat that they are more reminiscent of tables than containers. Since the Greco-Roman religion knew a variety of ritual cleanings of the body or just the hands and feet, a relatively flat shape is not uncommon. In order to meet the needs of the public and private cult of purification, appropriate water basins were made and installed. In contrast to the Jewish stone vessels, Roland Deines assumes that the stone had no special ritual function in the Greco-Roman area.

Occurrence

Significant deposits can be found in Egypt, e.g. in the region around Lake Victoria. B. in the district of Kisii , South Africa, Brazil, China, France, Finland (especially in the area around Nunnanlahti), India (where it was mainly used in medieval Hoysala architecture and sculpture), Italy, Canada, Norway, Austria ( Rabenwald: largest talc deposit in Central Europe), Russia, Switzerland and the Ukraine. In Germany, soapstone was quarried until a few years ago in the Johanneszeche in the district of the same name in Wunsiedel in Upper Franconia ; the company was also known for its rare soapstone / quartz pseudomorphoses . The soapstone used to build stoves is mainly obtained in Finland and Brazil.

Many deposits in the southern Alpine regions have been exploited for traditional kiln construction and pot production in the past centuries. Sometimes the extraction had to be carried out under adventurous circumstances on dangerous slopes or in risky secured small tunnels. Numerous deposits are completely exhausted or can hardly be found. Only a few deposits are still active.

The Ørslev stone bowl is a specimen from Norway.

use

Commodities

Cylinder seal and clay impression, steatite, Assyrian Empire, 9th – 8th centuries. Century BC Chr.

Soapstone has been used to manufacture everyday objects for thousands of years. The Hittites used soapstone to make cylinder seals . In Iran there are vessels made of steatite from the 3rd millennium BC. In the late Minoan - Mycenaean culture, seals and vessels were made from soapstone. The upper part of a funnel-shaped drinking vessel is exhibited in the Archaeological Museum of Heraklion . Numerous soapstone finds have also been found in Egypt. In China, the cheap soapstone served as a substitute for the rarer jade for the production of richly decorated sculptures and everyday objects in earlier and more recent times .

In Zimbabwe there are figures from the 11th to 15th centuries. In Liberia and Sierra Leone , so-called nomoli were found, which in the 17th century BC. Chr. In Mende country to have incurred.

In the past, the Canadian Inuit only made oil lamps from soapstone, but towards the end of the 19th century they began to create small sculptures, which quickly gained international recognition and became an important source of income.

The Vikings used soapstone to make everyday objects. Finds in Haithabu and grave attachments in Norway show that soapstone was used for vessels, spindle whorls , weights and flywheels for wood drills. These were decorated with ornamental incisions or runes.

The stone was also used as a casting mold for jewelry as well as bronze and silver bars, as it is a fireproof material.

Soapstone pot with lid, new production based on a historical model

In some regions soapstone stoves are traditionally used, which are characterized by an extraordinarily long heat storage capacity. These soapstones are hard and unsuitable for sculptural design. Well-known regions for this type of furnace are Norway, Finland, southern Switzerland and northern Italy. In the Valais village of Champsec there is a soapstone museum ( Musée de la Pierre Ollaire ) because there is a historically significant deposit in the Val de Bagnes . Soapstone stoves were made from their material .

Because of its heat resistance, soapstone has also been used for cookware since ancient times .

Industrial use

Ground soapstone ( talc ) is used industrially in the glass, paint and paper industry , as a lubricant , scouring agent, separating agent in cables and between tires and tubes, basic material for cosmetics, pharmaceuticals, baby powder, body powder, in the food industry as well as in the plastics, Used in ceramic, porcelain and auto industries.

Soapstone used to be used to make isolators and control panels.

For mechanically and thermally highly stressed insulators such as base point insulators for self-radiating transmission masts , fuses or overhead line insulators , however, steatite - a technical ceramic - is used , which is essentially burned from ground soapstone .

Due to its refractory properties, soapstone is a good raw material for the production of electrical ceramics such as insulators and furnace cladding .

Arts and crafts

Chinese relief "Spring returns to earth", artist: Zheng Shibin

Soapstone sculpture Freundeskreis by Kevin Wiersch

In sculpture , soapstone (similar to alabaster) is considered a pure “indoor” stone because of its poor weather resistance. Compact colored stones are preferred for the production of sculptures . They are easy to work with and easy to polish. The same tools are usually used for rough shaping as for woodworking ( carving knife , saw , rasp , file, etc.), and fine sanding is also possible with commercially available materials such as sandpaper , steel wool and polishing paste . In order to obtain a permanent shine, the finished workpieces are usually finally polished with wax or oil, which at the same time seals the surface.

Since the stone is very soft - it can be scratched with a fingernail - it is easy to work with, but the resistance of the polished surface is extremely low. It is often used in art education and art therapy .

hazards

Asbestos fibers can be found in soapstone . In general, valley deposits of carbonate origin are asbestos-free. Serpentinite deposits could contain asbestos, but these are no longer mined worldwide. Since inhaled asbestos fibers u. a. Can cause lung tumors, only soapstone for which a traceable and documented proof of origin has been provided should be used for the sculptural design. When used in industrial products, clearance certificates are required before use. Soapstone, which contains asbestos, is only harmful to health if the asbestos z. B. is released by machining.

Certified asbestos-free soapstone can also contain asbestos, which is why soapstone cannot be processed in German schools.

literature

• Author collective: 2000 anni di pietra ollare . In: Dipartimento dell'Ambiente, Ufficio Monumenti Storici (ed.): Quaderni d'informazione . No. 11 . Ufficio Musei, Bellinzona 1986.
• J. Reinhard Blum: Lithurgics or minerals and types of rock according to their application in economic, artistic and technical terms, dealt with systematically . E. Schweizerbart's publishing house, Stuttgart 1840.
• Roland Deines: Jewish stone vessels and Pharisaic piety. An archaeological-historical contribution to the understanding of Joh 2,6 and the Jewish purity halacha at the time of Jesus (=  Scientific investigations on the New Testament . Volume 52 ). JCB Mohr, Tübingen 1993, ISBN 3-16-146022-7 .
• Isolde Hausner, Peter Wiesinger (ed.): German word research as cultural history (=  Austrian academy of science, philosophical-historical class, session reports . Volume 720 ). Publishing house of the Austrian Academy of Sciences, Vienna 2003, ISBN 3-7001-3399-5 .
• Martin Okrusch, Siegfried Matthes: Mineralogy: An introduction to special mineralogy, petrology and deposit science . 7th edition. Springer Verlag, Berlin / Heidelberg / New York 2005, ISBN 3-540-23812-3 , pp. 101 (talk).
• F. de Quervain: The usable rocks of Switzerland . Kümmerly & Frey, Geographischer Verlag, Bern 1969.
• Wolfhard Wimmenauer: Petrography of igneous and metamorphic rocks . Ferdinand Enke Verlag, Stuttgart 1985, ISBN 3-432-94671-6 .
• Ludwig Friedrich Wolfram: Complete textbook of the entire architecture . In: Doctrine of natural building materials . First Volume: First Section. From natural building materials. . Carl Hoffmann / Carl Gerold'sche Buchhandlung, Stuttgart / Vienna 1833 ( reader.digitale-sammlungen.de ).
• Safety in Education Policy (Risu) . 2013.

Web links

Commons : Soapstone  - collection of pictures, videos and audio files

Individual evidence

1. ↑ Mineralienatlas: Soapstone or Mineralienatlas: Talk (Wiki)
2. ^ Wolfhard Wimmenauer : Petrography. P. 287.
3. ↑ Duden - The great foreign dictionary. Bibliographisches Institut, Mannheim 3rd edition 2003.
4. ^ Marino Lepori: Escursione fra le fonti scritte. 2000 anni di pietra ollare. Bellinzona 1986, p. 3.
5. ^ Marino Lepori: Escursione fra le fonti scritte. 2000 anni di pietra ollare. Bellinzona 1986, p. 14.
6. ↑ Roland Deines: Jewish stone vessels and Pharisaic piety. P. 55.
7. ^ Wilhelm Meyer: Geology of the Eifel. E. Schweizerbart'sche publishing bookstore.
8. ^ Emil Öhmann: On the linguistic influence of Italy on Germany. In: Neuphilologische Mitteilungen. (NphM) 1941, p. 111.
9. ↑ Max Pfister: Germanic-Romance cultural relations based on Northern Italian and Ladin vocabulary . In: Deutsche Wortforschung als Kulturgeschichte, Vienna 2003 (Österr. Akadem. D. Wiss., Philosophical-historical class, session reports, 720th volume).
10. ↑ Isolde Hausner, Peter Wiesinger (Ed.): German word research as cultural history. Vienna 2003 (Austrian Academic of Science, Philosophical-Historical Class, Meeting Reports, Volume 720).
11. ↑ Harald Olbrich (Ed.): Lexicon of Art. Architecture, fine arts, applied arts, industrial design, art theory. Volume 4. EA Seemann, Leipzig 1992.
12. ↑ Wolfram, 1833, p. 86.
13. ↑ Blum, 1840, pp. 97, 98
14. ↑ Cato: De Agri Cultura X 4, XI 3; XIII 2
15. ↑ Ginouvès, ibid. 67 f. 89 ff. And pl. XX: 59-62; XXIII: 69 f.
16. ↑ Roland Deines: Jewish stone vessels and Pharisaic piety. Pp. 56-57.
17. ↑ The Johanneszeche mine in Göpfersgrün and the rare minerals found in it
18. ↑ Entry ( Memento of the original from January 29, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on the website of the municipality of Bagnes (accessed on 23 January 2010)  
19. ↑ Breviary TECHNICAL CERAMICS - Steatite
20. ↑ Hans Joachim Bezler, Ludger Hohenberger, Robert Kellner, Axel Piechocki, Rainer Radtke, Uwe Ritzmann, Peter Ruck: Guideline for Safety in Teaching (RiSU). Recommendation of the Conference of Ministers of Education. (PDF, 3.93 MB) p. 25 , accessed on December 16, 2014 : “Asbestos-containing work equipment and aids are to be replaced in order to exclude hazards from asbestos fibers. ... as well as the processing of soapstone is not permitted because it may contain asbestos. ... Investigations of material samples have shown that commercially available soapstone contains asbestos. This was also the case to a considerable extent for soapstone samples for which the suppliers had certified asbestos-free. If necessary, proper disposal must be ensured. "