Soapstone (also known as steatite or soaprock) is a talc-schist, which is a type of metamorphic rock. It is composed largely of the magnesium-rich mineral talc. It is produced by dynamothermal metamorphism and metasomatism, which occur in subduction zones, changing rocks by heat and pressure, with influx of fluids but without melting. It has been a carving medium for thousands of years.
The definitions of the terms "steatite" and "soapstone" vary with the field of study. In geology, steatite is a rock that is, to a very large extent, composed of talc. The mining industry defines steatite as a high-purity talc rock that is suitable for the manufacturing of, for example, insulators; the lesser grades of the mineral can be called simply "talc rock". Steatite can be used both in lumps ("block steatite", "lava steatite", "lava grade talc"), and in the ground form. While the geologists logically will use "steatite" to designate both forms, in the industry, "steatite" without additional qualifications typically means the steatite that is either already ground or to be used in the ground form in the future. If the ground steatite is pressed together into blocks, these are called "synthetic block steatite", "artificial block steatite", or "artificial lava talc". [1]
In industrial applications soapstone refers to dimension stone that consists of either amphibole-chlorite-carbonate-talc rock, talc-carbonate rock, or simply talc rock and is sold in the form of sawn slabs. "Ground soapstone" sometimes designates the ground waste product of the slab manufacturing. [1]
Petrologically, soapstone is composed predominantly of talc, with varying amounts of chlorite and amphiboles (typically tremolite, anthophyllite, and cummingtonite, hence its obsolete name, magnesiocummingtonite), and traces of minor iron-chromium oxides. It may be schistose or massive. Soapstone is formed by the metamorphism of ultramafic protoliths (e.g. dunite or serpentinite) and the metasomatism of siliceous dolomites.
By mass, "pure" steatite is roughly 63.37% silica, 31.88% magnesia, and 4.74% water. [2] It commonly contains minor quantities of other oxides such as CaO or Al2O3.
Pyrophyllite, a mineral very similar to talc, is sometimes called soapstone in the generic sense, since its physical characteristics and industrial uses are similar, [3] and because it is also commonly used as a carving material. However, this mineral typically does not have such a soapy feel as soapstone.
Soapstone is relatively soft because of its high talc content—talc has a definitional value of 1 on the Mohs hardness scale. Softer grades may feel similar to soap when touched, hence the name. No fixed hardness is given for soapstone because the amount of talc it contains varies widely, from as little as 30% for architectural grades such as those used on countertops, to as much as 80% for carving grades.
Soapstone is easy to carve; it is also durable and heat-resistant and has a high heat storage capacity. It has therefore been used for cooking and heating equipment for thousands of years. [4]
Soapstone is often used as an insulator for housing and electrical components, due to its durability and electrical characteristics and because it can be pressed into complex shapes before firing. Soapstone undergoes transformations when heated to temperatures of 1,000–1,200 °C (1,830–2,190 °F) into enstatite and cristobalite; on the Mohs scale, this corresponds to an increase in hardness to 5.5–6.5. [5] The resulting material, harder than glass, is sometimes called "lava". [6]
Ancient Egyptian scarab signets and amulets were most commonly made from glazed steatite. [7] The Yoruba people of West Nigeria used soapstone for several statues, most notably at Esie, where archaeologists have uncovered hundreds of male and female statues about half of life size. The Yoruba of Ife also produced a miniature soapstone obelisk with metal studs called "the staff of Oranmiyan".
Native Americans have used soapstone since the Late Archaic Period. During the Archaic archaeological period (8000-1000 BC), bowls, cooking slabs, and other objects were made from soapstone. [8] Use of soapstone in native American cultures continue to the modern day. Later, other cultures carved soapstone smoking pipes, a practice that continues today. The soapstone's low heat conduction allows for prolonged smoking without the pipe heating up uncomfortably. [9]
Indigenous peoples of the Arctic have traditionally used soapstone for carvings of both practical objects and art. The qulliq, a type of oil lamp, is carved out of soapstone and used by the Inuit, Chukchi, and Yupik peoples. This kind of lamp was the single most important article of furniture for the Inuit in their dwellings.
In the modern period, soapstone is commonly used for carvings in Inuit art. [10]
In the United States, locally-quarried soapstone was used for gravemarkers in 19th century northeast Georgia, around Dahlonega, and Cleveland as simple field stone and "slot and tab" tombs. Small blocks of soapstone (8" x 10" x 1") were also heated on the cookstove or near the fire and used to warm cold bedclothes or to keep hands and feet cozy while sleighing.
The ancient trading city of Tepe Yahya in southeastern Iran was a center for the production and distribution of soapstone in the 5th to 3rd millennia BC. [11]
Soapstone has been used in India as a medium for sculptures since at least the time of the Hoysala Empire, the Western Chalukya Empire and to an extent Vijayanagara Empire. [12] Even earlier, steatite was used as the substrate for Indus-Harappan seals. [13] [14] After carving, the seals were heated above 1,000 °C (1,830 °F) for several days to make them hard and durable to make the final seals used for making impressions on clay.
In China, during the Spring and Autumn Period (771–476 BC), soapstone was carved into ceremonial knives. [15] Soapstone was also used to carve Chinese seals.
Soapstone was used as a writing pencil in Myanmar as early as the 11th-century Pagan period. After that, it was still used as a pencil to write on Black Parabaik until the end of the Mandalay period (19th century).
Pipes and decorative carvings of local animals were made out of soapstone by Australian Aboriginal artist Erlikilyika (c.1865–c.1930) in Central Australia. [16]
The Minoan civilization on Crete used soapstone. At the Palace of Knossos, a steatite libation table was found. [17] Soapstone is relatively abundant in northern Europe. Vikings hewed soapstone directly from the stone face, shaped it into cooking pots, and sold these at home and abroad. [18] In Shetland, there is evidence that these vessels were used for processing marine and dairy fats. [19] Several surviving medieval buildings in northern Europe are constructed with soapstone, amongst them Nidaros Cathedral. [4]
In modern times, soapstone is most commonly used for architectural applications, such as counter tops, floor tiles, showerbases, and interior surfacing.
Soapstone is sometimes used for construction of fireplace surrounds, cladding on wood-burning stoves, [20] [21] and as the preferred material for woodburning masonry heaters because it can absorb, store, and evenly radiate heat due to its high density and magnesite (MgCO3) content. [20] [21] It is also used for countertops and bathroom tiling because of the ease of working the material and its property as the "quiet stone". A weathered or aged appearance occurs naturally over time as the patina is enhanced.
Soapstone can be used to create molds for casting objects from soft metals, such as pewter or silver. The soft stone is easily carved and is not degraded by heating. The slick surface of soapstone allows the finished object to be easily removed.
Welders and fabricators use soapstone as a marker due to its resistance to heat; it remains visible when heat is applied. It has also been used for many years by seamstresses, carpenters, and other craftspeople as a marking tool, because its marks are visible but not permanent.
Resistance to heat made steatite suitable for manufacturing gas burner tips, spark plugs, and electrical switchboards. [6]
Steatite ceramics are low-cost biaxial porcelains of nominal composition (MgO)3(SiO2)4. [22] Steatite is used primarily for its dielectric and thermally-insulating properties in applications such as tile, substrates, washers, bushings, beads, and pigments. [23] It is also used for high-voltage insulators, which have to stand large mechanical loads, such as insulators of mast radiators.
Soapstone continues to be used for carvings and sculptures by artists and indigenous peoples. In Brazil, especially in the state of Minas Gerais, the abundance of soapstone mines allow local artisans to craft pots, pans, wine glasses, statues, jewel boxes, coasters, and vases from soapstone. These handicrafts are commonly sold in street markets found in cities across the state. Some of the oldest towns, notably Congonhas, Tiradentes, and Ouro Preto, still have some of their streets paved with soapstone from colonial times.
Architectural soapstone is mined in Canada, Brazil, India, and Finland and imported into the United States. [24] Active North American mines include one south of Quebec City with products marketed by Canadian Soapstone, the Treasure and Regal mines in Beaverhead County, Montana mined by the Barretts Minerals Company, and another in central Virginia operated by the Alberene Soapstone Company.
Mining to meet worldwide demand for soapstone is threatening the habitat of India's tigers. [25]
Soapstones can be put in a freezer and later used in place of ice cubes to chill alcoholic beverages without diluting. Sometimes called whiskey stones, these were first introduced around 2007. [26] Most whiskey stones feature a semipolished finish, retaining the soft look of natural soapstone, while others are highly polished.
People can be exposed to soapstone dust in the workplace via inhalation and skin or eye contact. Exposure above safe limits can lead to symptoms including coughing, shortness of breath, cyanosis, crackles, and pulmonary heart disease. Due to the potential presence of tremolite and crystalline silica in the dust, precautions should be taken to avoid occupational diseases such as asbestosis, silicosis, mesothelioma, and lung cancer. [27]
The Occupational Safety and Health Administration has set the legal limit (permissible exposure limit) for soapstone exposure in the workplace as 20 million particles per cubic foot over an 8-hour workday. The National Institute for Occupational Safety and Health has set a recommended exposure limit of 6 mg/m3 total exposure and 3 mg/m3 respiratory exposure over an 8-hour workday. At levels of 3000 mg/m3, soapstone is immediately dangerous to life and health. [28]
The local names for the soapstone vary: in Vermont, "grit" is used, in Georgia "white-grinding" and "dark-grinding" varieties are distinguished, and California has "soft", "hard", and "blue" talc. [29] Also:
Marble is a metamorphic rock consisting of carbonate minerals (most commonly calcite (CaCO3) or dolomite (CaMg(CO3)2)) that have recrystallized under the influence of heat and pressure. It has a crystalline texture, and is typically not foliated (layered), although there are exceptions.
Talc, or talcum, is a clay mineral composed of hydrated magnesium silicate, with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent and lubricant. It is an ingredient in ceramics, paints, and roofing material. It is a main ingredient in many cosmetics. It occurs as foliated to fibrous masses, and in an exceptionally rare crystal form. It has a perfect basal cleavage and an uneven flat fracture, and it is foliated with a two-dimensional platy form.
Hoysala architecture is the building style in Hindu temple architecture developed under the rule of the Hoysala Empire between the 11th and 14th centuries, in the region known today as Karnataka, a state of India. Hoysala influence was at its peak in the 13th century, when it dominated the Southern Deccan Plateau region. Large and small temples built during this era remain as examples of the Hoysala architectural style, including the Chennakesava Temple at Belur, the Hoysaleswara Temple at Halebidu, and the Kesava Temple at Somanathapura. These three temples were accorded UNESCO world heritage site status in 2023. Other examples of Hoysala craftsmanship are the temples at Belavadi, Amruthapura, Hosaholalu, Mosale, Arasikere, Basaralu, Kikkeri and Nuggehalli. Study of the Hoysala architectural style has revealed a negligible Indo-Aryan influence while the impact of Southern Indian style is more distinct.
Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade, regional metamorphism. It is the finest-grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.
A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to manage their safety risks and reduce their environmental impact.
Quartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of hematite. Other colors, such as yellow, green, blue and orange, are due to other minerals.
Pyrophyllite is a phyllosilicate mineral composed of aluminium silicate hydroxide: Al2Si4O10(OH)2. It occurs in two forms (habits): crystalline folia and compact masses; distinct crystals are not known.
Stone carving is an activity where pieces of rough natural stone are shaped by the controlled removal of stone. Owing to the permanence of the material, stone work has survived which was created during our prehistory or past time.
Serpentinite is a metamorphic rock composed predominantly of one or more serpentine group minerals formed by near to complete serpentinization of mafic to ultramafic rocks. Its name originated from the similarity of the texture of the rock to that of the skin of a snake. Serpentinite has been called serpentine or serpentine rock, particularly in older geological texts and in wider cultural settings.
Dimension stone is natural stone or rock that has been selected and finished to specific sizes or shapes. Color, texture and pattern, and surface finish of the stone are also normal requirements. Another important selection criterion is durability: the time measure of the ability of dimension stone to endure and to maintain its essential and distinctive characteristics of strength, resistance to decay, and appearance.
A countertop, also counter top, counter, benchtop, worktop or kitchen bench, bunker is a raised, firm, flat, and horizontal surface. They are built for work in kitchens or other food preparation areas, bathrooms or lavatories, and workrooms in general. The surface is frequently installed upon and supported by cabinets, positioned at an ergonomic height for the user and the particular task for which it is designed. A countertop may be constructed of various materials with different attributes of functionality, durability and aesthetics, and may have built-in appliances, or accessory items relative to the intended application.
Vijayanagara architecture of 1336–1565 CE was a notable building idiom that developed during the rule of the imperial Hindu Vijayanagara Empire. The empire ruled South India, from their regal capital at Vijayanagara, on the banks of the Tungabhadra River in modern Karnataka, India. The empire built temples, monuments, palaces and other structures across South India, with the largest concentration in its capital. The monuments in and around Hampi, in the Vijayanagara district, are listed as a UNESCO World Heritage Site.
A stone sculpture is an object made of stone which has been shaped, usually by carving, or assembled to form a visually interesting three-dimensional shape. Stone is more durable than most alternative materials, making it especially important in architectural sculpture on the outside of buildings.
Asbestos is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere by abrasion and other processes. Inhalation of asbestos fibres can lead to various dangerous lung conditions, including mesothelioma, asbestosis, and lung cancer. As a result of these health effects, asbestos is considered a serious health and safety hazard.
Hardstone carving, in art history and archaeology, is the artistic carving of semi-precious stones, such as jade, rock crystal, agate, onyx, jasper, serpentinite, or carnelian, and for objects made in this way. Normally the objects are small, and the category overlaps with both jewellery and sculpture. Hardstone carving is sometimes referred to by the Italian term pietre dure; however, pietra dura is the common term used for stone inlay work, which causes some confusion.
Hardstone is a non-scientific term, mostly encountered in the decorative arts or archaeology, that has a similar meaning to semi-precious stones, or gemstones. Very hard building stones, such as granite, are not included in the term in this sense, but only stones which are fairly hard and regarded as attractive – ones which could be used in jewellery. Hardstone carving is the three-dimensional carving for artistic purposes of semi-precious stones such as jade, agate, onyx, rock crystal, sard or carnelian, and a general term for an object made in this way. Two-dimensional inlay techniques for floors, furniture and walls include pietre dure, opus sectile, and medieval Cosmatesque work – these typically inlay hardstone pieces into a background of marble or some other building stone.
Catpund is a quarry site in Shetland, Scotland, where steatite vessels were cut from the rock from prehistory onwards. The quarrying marks are still visible today.
Stone carving in Odisha is the ancient practice of sculpting stone into art and utilitarian objects. It is an ancient practice in the Indian state of Odisha. Stone carving is practiced by artisans mainly in Puri, Bhubaneswar and Lalitgiri in the Cuttack district, though some carvings can be found in Khiching in the Mayurbhanj District. Stone carving is one of the major handcrafts of Odisha. The art form primarily consists of custom carved works, with the Sun Temple of Konark and its intricate sculpture and delicate carvings on the red vivid sandstone exemplifying the practice. Other noteworthy monuments include the Stupas of Udayagiri and Ratnagiri and the temples at Jagannath, Lingaraj, Mukteshwar and as well as other temples in the region.
In the Kisii region in Kenya, soapstone is mined in the town of Tabaka. It has been at the heart of industry and culture, with its malleability allowing for the carving of a variety of items ranging from common household items to ornaments and other décor items, all of which have found their way into the commercial space, birthing the aforementioned 'industry' around the mining and processing of the ore – largely centered in Tabaka. In its finely milled form, soapstone has been found to have various commercial uses outside carving.
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