حجر البرم
بفتح باء موحده و راء مهمله و الف و میم
ماهیت آن
سنکی است سیاه که از ان دیک* و ظروف می سازند و در
خراسان بسیار است
افعال و خواص آن
جهت تقویت لثۀ دندان و نزف الدم مؤثر است
*سنگ «هرکاره» یا
«سنگ دیگ» نوعی سنگ دگرگونی از گروه تالک شیست «Talc schist» هاست
که از تغییر سنگ‌های سرپانتین تولید می‌شود. این سنگ به دلیل ساختار چرب و صابونی که
دارد به «سنگ صابونی**» هم مشهور است و به دلیل ساختار نرم آن به راحتی تراشیده شده
و شکل می‌گیرد.
این سنگ هادی خوبی
برای حرارت نبوده و از آن برای ساخت ظروف مخصوص پخت و پز استفاده می‌شود که این امکان
را می‌دهد غذا با حرارت کم و طولانی مدت پخته شود. دیگ‌ها و ظروف ساخته شده از این
سنگ برای پخت غذاهای سنتی ایرانی مانند دیزی و انواع خورشت بسیار مطلب است.
معادن این نوع سنگ
در همه جای جهان یافت می‌شود و در ایران نیز معادن آن در زنجان، سیستان، کرمان، خوی،
ماکو، سبزوار، تربت حیدریه و بیرجند وجود دارد اما استخراج عمده و انبوه آن از معادن
اطراف مشهد مقدس است.
گفته می‌شود در سایر
مناطق، به جز سنگ مشهد، با توجه به سختی بیش از اندازه سنگ و عدم شکل‌پذیری، امکان
تولید انبوه و باکیفیت محصولات سنگی وجود ندارد. مهم‌ترین معادن سنگ مشهد عبارتند از
«بزه اوشر» Baze ušar، «بزه انقى» Baze annaqi، «بزه زکریا» Baze zakaria و «بزه نجفى» Baze najafi که عموماً در جنوب
شهر مشهد واقع هستند.
تولید ظروف سنگی و
مجسمه از این سنگ در بسیاری از کشورهای جهان مانند هند، برزیل، چین و ... از دیرباز
انجام می‌شده است اما جالب است بدانید بسیاری از قدیمی‌ترین ظروف و آثار ساخته‌شده
این سنگ در جهان در سایت‌های باستان‌شناسی کرمان مانند «تپه یحیی»، «شهداد» و «جیرفت»
یافت شده‌اند. ظروف یافت‌شده از این سایت‌های باستانی مربوط به اوایل هزاره سوم پیش
از میلاد است.
این سنگ امروزه نیز در بسیاری از کشورها برای تولید
ظروف و مجسمه و سوغات استفاده می‌شود و شاید مثال شناخته شده از کاربرد امروزه این
سنگ، مجمسه «مسیح نجات‌دهنده» در شهر ریودوژانریو با ارتفاعی بالغ بر ۳۷ متر باشد.
** Soapstone (also
known as steatite, or soaprock) is a talc-schist, which is a type ofmetamorphic rock. It is largely composed of the
mineral talc and is thus rich inmagnesium. It is produced by dynamothermal metamorphism and metasomatism, which occurs in the zones where tectonic plates are subducted, changing rocks by heat and pressure, with
influx of fluids, but without melting. It has been a medium for carving for
thousands of years.
Contents
[show]
A
block of talc
Petrologically, soapstone is composed
dominantly of talc, with varying amounts ofchlorite and amphiboles (typically tremolite, anthophyllite, and cummingtonite, obsolete name:
magnesiocummingtonite), and trace to minor FeCr-oxides.
It may be schistose or massive. Soapstone is formed by the
metamorphism of ultramaficprotoliths (e.g. dunite or serpentinite) and the metasomatism of siliceousdolostones.
By mass, steatite is
approximately 67% silica and 33% magnesia, and may contain 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,[citation needed] 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 having a definitional
value of 1 on the Mohs
hardness scale. Softer grades may feel soapy when touched, hence the
name. There is no fixed hardness 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. Common,
non-architectural grades of soapstone can just barely be scratched with a
fingernail and are thus considered to have a hardness of 2.5 on the Mohs scale.[1] If a candidate rock cannot be scratched with a knife blade
(hardness of 5.5), it is not soapstone.
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
1000–1200 °C into enstatite and cristobalite; in the Mohs scale, this
corresponds to an increase in hardness to 5.5–6.5.[2]
The
21st-century BCEstatue of Iddi-Ilum of Mari is made of soapstone
Soapstone is used for
inlaid designs, sculpture, coasters, and kitchen countertops and sinks. The Inuit often
use soapstone for traditional carvings. Some Native
American tribes and bands make bowls, cooking slabs, and other
objects from soapstone; historically, this was particularly common during the
Late Archaic
archaeological period.[3]
Locally quarried
soapstone was used for gravemarkers in 19th century northeast Georgia,
US, around Dahlonega,
and Cleveland, as
simple field stone and "slot and tab" tombs.
Vikings hewed
soapstone directly from the stone face, shaped it into cooking-pots, and sold
these at home and abroad.[4]
Soapstone is sometimes
used for construction of fireplace surrounds, cladding on metal woodstoves, 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. It is also used for counter tops
and bathroom tiling because of the ease of working the material and its
property as the "quiet stone." A weathered or aged appearance will
occur naturally over time as the patina is enhanced. Applying mineral oil
simply darkens the appearance of the stone; it does not protect it in any way.[citation needed]
Tepe Yahya, an ancient trading city in
southeastern Iran, was a center for the production and
distribution of soapstone in the 5th–3rd millennia BC.[5] It was also used in MinoanCrete.
At the Palace of Knossos, archaeological recovery has included a
magnificentlibation table made of steatite.[6] The Yoruba of West Nigeria utilized 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 superstitiously "the
staff of Oranmiyan"
The
outer layers of the Christ the
Redeemer sculpture in Rio de Janeiroare made of soapstone.
Soapstone has been
used in India for centuries as a medium for
carving. Mining to meet world-wide demand for soapstone is threatening the
habitat of India's tigers.[7]
In Brazil, especially
in Minas Gerais, due
to the abundance of soapstone mines in that Brazilian state, local artisans
still craft objects from that material, including pots and pans, wine glasses,
statues, jewel boxes, coasters, vases. 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.
Some Native Americans
use soapstone for smoking pipes;
numerous examples have been found among artifacts of different cultures and are
still in use today. Its low heat conduction allows for prolonged smoking without
the pipe's heating up uncomfortably.[8]
Some premium wood
fired heating stoves are made of soapstone to take advantage of its useful
thermal and fire resistant properties.
Soapstone is also used
to carve Chinese seals.
Currently, soapstone
is most commonly used for architectural applications, such as counter tops and
interior surfacing. There is currently only one active North American soapstone
mine. That mine is found in Central Virginia and is operated by the Alberene
Soapstone Company. All other architectural soapstone is mined in Brazil, India
and Finland and imported into the United States.[9]
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 craftsmen as a marking tool because its marks are visible
and not permanent.
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.
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. Most whiskey stones feature a semi-polished finish,
retaining the soft look of natural soapstone, while others are highly polished.
Steatite ceramics are low-cost biaxial porcelains of nominal composition (MgO)3(SiO2)4.[10] Steatite is used primarily for itsdielectric and thermal insulating
properties in applications such as tile, substrates, washers, bushings, beads
and pigments.[11]
People can be exposed
to soapstone in the workplace by breathing it in, skin contact, or eye contact.
The Occupational
Safety and Health Administration (OSHA) has set the legal limit
(Permissible
exposure limit) for soapstone exposure in the workplace as 20 mppcf
over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH)
has set a Recommended
exposure limit (REL) 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.[12]
·
Combarbalite stone, exclusively mined in Combarbalá, Chile,
is known for its many colors. While they are not visible during mining, they
appear after refining.
·
Palewa and gorara stones are types of Indian soapstone.
·
12th century Byzantine relief of Saint George
and the Dragon
·
·
Soapstone slot & tab tomb in Dahlonega, Georgia,
US.
·
An Egyptian carved and glazed steatite scarabamulet.
·
Steatite scarab. The Walters Art
Museum.
2.
Jump up^ "Some Important Aspects of the Harappan Technological
Tradition," Bhan KK, Vidale M and Kenoyer JM, in Indian
Archaeology in Retrospect/edited by S. Settar and Ravi Korisettar, Manohar
Press, New Delhi, 2002.
3.
Jump up^ Kenneth E. Sassaman (1993-03-30). Early Pottery in
the Southeast: Tradition and Innovation in Cooking Technology. University
Alabama Press. ISBN 978-0-8173-0670-0.
5.
Jump up^ "Tepe Yahya," Encyclopædia
Britannica, 2004. Britannica Concise Encyclopedia. 3 January
2004, Britannica.com
7.
Jump up^ Barnett, Antony (2003-06-22). "West's love of talc threatens India's tigers". The
Guardian. London. Retrieved 2007-01-09.
8.
Jump up^ Witthoft, J.G., 1949, "Stone Pipes of the Historic
Cherokees", Southern Indian Studies 1(2):43–62.
9.
Jump up^ "Soapstone gives countertops, tiles a look that's
both new and old". The Washington Post. Retrieved 2014-01-11.
12. Jump up^ "CDC - NIOSH Pocket Guide to Chemical Hazards -
Soapstone (containing less than 1% quartz)".www.cdc.gov.
Retrieved 2015-11-21.
