Emery, or corundite, is a dark granular rock used to make an abrasive powder. The rock largely consists of

corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium, and chromium. It is a rock (geology), rock-forming mineral. It is a naturally transparency and translucency, transparent material, but ...

(

aluminium oxide Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several Aluminium oxide (compounds), aluminium oxides, and specifically identified as alum ...

), mixed with other minerals. Industrial emery may contain a variety of other minerals and synthetic compounds. Crushed or naturally eroded emery (known as ''black sand'') is used as an abrasive. Turkey and Greece are the main suppliers of the world's emery.

Description

Emery is a granular rock used to make an abrasive powder. It largely consists of

(

), mixed with other minerals such as the iron-bearing

spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , a diminutive form of ''spine,'' in reference to its pointed crystals. Prop ...

s, hercynite, and

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

, and also

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at vis ...

( titania). Industrial emery may contain a variety of other minerals and synthetic compounds such as magnesia,

mullite Mullite or porcelainite is a rare silicate mineral formed during contact metamorphism of clay minerals. It can form two stoichiometric forms: 3 Al2 O32 SiO2 or 2Al2O3 SiO2. Unusually, mullite has no charge-balancing cations present. As a result ...

, and

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

. Emery is black or dark grey in colour, less dense than translucent-brown corundum with a

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of between 3.5 and 3.8. Because it can be a mixture of minerals, no definite

Mohs hardness The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fair ...

can be assigned: the hardness of corundum is 9 and that of some spinel-group minerals is near 8, but the hardness of others such as magnetite is near 6.

Use

Crushed or naturally eroded emery (known as ''black sand'') is used as an abrasive—for example, on emery boards and emery cloth. It is also used as a traction enhancer in

asphalt Asphalt most often refers to: * Bitumen, also known as "liquid asphalt cement" or simply "asphalt", a viscous form of petroleum mainly used as a binder in asphalt concrete * Asphalt concrete, a mixture of bitumen with coarse and fine aggregates, u ...

and tarmac mixtures. A small quantity of emery is used in coated abrasive products, but its main use in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

is wear-resistant floors and pavements. Many tons are shipped to Asia to be used in grinding rice. Solomon's shamir, a substance used to cut stone during construction of the First Temple, was likely emery.

Harvest

Turkey and Greece are the main suppliers of the world's emery. These two countries produced about 17,500 tons of the mineral in 1987. The Greek island of

Naxos Naxos (; , ) is a Greek island belonging to the Cyclades island group. It is the largest island in the group. It was an important centre during the Bronze Age Cycladic Culture and in the Ancient Greek Archaic Period. The island is famous as ...

used to be the main source of this industrially important rock type. It has been mined on the eastern side of Naxos for well over two thousand years as mentioned by

Pliny the Elder Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...

's ''The Natural History'', book XXXVII, chp. 32. However, demand for emery has decreased with the development of

sintered Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, pla ...

carbide and oxide materials as abrasives.

Safety

In the United States, the

Occupational Safety and Health Administration The Occupational Safety and Health Administration (OSHA; ) is a regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. The United States Congress established ...

has set permissible exposure limits for emery in the workplace: TWA 15 mg/m³ total exposure and TWA 5 mg/m³ respiratory exposure.

References

External links

CDC - NIOSH Pocket Guide to Chemical Hazards
* {{ill, Emery mining in Waldthurn, de, Schmirgelabbau in Waldthurn, vertical-align=sup Aluminium minerals Abrasives Corundum varieties Oxide minerals Iron minerals

Description

Use

Harvest

Safety

See also

References

Further reading

External links