Moissanite
Encyclopedia
Moissanite ˈmɔɪsənaɪt originally referred to a rare mineral discovered by Henri Moissan
having a chemical formula SiC and various crystalline polymorphs
. Earlier, this material had been synthesized in the laboratory and named silicon carbide
(SiC).
while examining rock samples from a meteor crater located in Canyon Diablo
, Arizona
, in 1893. At first, he mistakenly identified the crystals as diamonds, but in 1904 he identified the crystals as silicon carbide. The mineral form of silicon carbide was named moissanite in honor of Moissan later on in his life. The discovery in the Canyon Diablo meteorite and other places was challenged for a long time as carborundum
contamination from human abrasive tools.
from a diamond mine in Yakutia in 1959, and in the Green River Formation
in Wyoming
in 1958. The existence of moissanite in nature was questioned even in 1986 by Charles Milton, an American geologist.
Moissanite, in its natural form, is very rare. It has only been discovered in a small variety of places from upper mantle
rock to meteorite
s. Discoveries have shown that moissanite occurs naturally as inclusions in diamonds, xenolith
s, and ultramafic rocks such as kimberlite
and lamproite
. They have also been identified in carbonaceous chondrite
meteorites as presolar grains
.
stars. SiC is commonly found around these stars as deduced from their infrared spectra.
. Years later, Acheson produced viable minerals that could substitute diamond as an abrasive and cutting material. This was possible as moissanite is one of the hardest substances known, with a hardness below that of diamond
and comparable with those of cubic boron nitride
and boron
. Since naturally occurring moissanite is so rare, lab-grown moissanite is the only commercially viable version of the mineral. More recently, pure synthetic Moissanite has been made from thermal decomposition of the preceramic polymer poly(methylsilyne), requiring no binding matrix (e.g. cobalt metal powder).
.
. Its ethical production, however, does make it a popular alternative to diamonds. In many developed countries, the use of moissanite in jewelry has been patented; these patents expire in 2015.
Because of its hardness, it is useful for high-pressure experiments (e.g., using diamond anvil cell
) competing there with diamond. Large diamonds, used for anvils, are prohibitively expensive. Therefore for large-volume experiments, synthetic moissanite is a more realistic choice. Synthetic moissanite is also interesting for electronic
and thermal applications because its thermal conductivity
is similar to that of diamonds. High power SiC electronic devices are expected to play an enabling and vital role in the design of protection circuits used for motors, actuator
s, and energy storage or pulse power systems.
Henri Moissan
Ferdinand Frederick Henri Moissan was a French chemist who won the 1906 Nobel Prize in Chemistry for his work in isolating fluorine from its compounds.-Biography:...
having a chemical formula SiC and various crystalline polymorphs
Polymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
. Earlier, this material had been synthesized in the laboratory and named silicon carbide
Silicon carbide
Silicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...
(SiC).
Background
Mineral moissanite was discovered by Henri MoissanHenri Moissan
Ferdinand Frederick Henri Moissan was a French chemist who won the 1906 Nobel Prize in Chemistry for his work in isolating fluorine from its compounds.-Biography:...
while examining rock samples from a meteor crater located in Canyon Diablo
Canyon Diablo (canyon)
Canyon Diablo is a canyon north of Two Guns in Northern Arizona. It is located in the Navajo Indian Reservation.The canyon passes three miles west of Meteor Crater. The community of Canyon Diablo, Arizona on the edge of the canyon about 12 miles northwest of the crater was the closest community...
, Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, in 1893. At first, he mistakenly identified the crystals as diamonds, but in 1904 he identified the crystals as silicon carbide. The mineral form of silicon carbide was named moissanite in honor of Moissan later on in his life. The discovery in the Canyon Diablo meteorite and other places was challenged for a long time as carborundum
Silicon carbide
Silicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...
contamination from human abrasive tools.
Geological occurrence
Until the 1950s no other source, apart from meteorites, had been encountered. Later moissanite was found as inclusion in kimberliteKimberlite
Kimberlite is a type of potassic volcanic rock best known for sometimes containing diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an diamond in 1871 spawned a diamond rush, eventually creating the Big Hole....
from a diamond mine in Yakutia in 1959, and in the Green River Formation
Green River Formation
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and...
in Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
in 1958. The existence of moissanite in nature was questioned even in 1986 by Charles Milton, an American geologist.
Moissanite, in its natural form, is very rare. It has only been discovered in a small variety of places from upper mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
rock to meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
s. Discoveries have shown that moissanite occurs naturally as inclusions in diamonds, xenolith
Xenolith
A xenolith is a rock fragment which becomes enveloped in a larger rock during the latter's development and hardening. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock during magma emplacement and eruption...
s, and ultramafic rocks such as kimberlite
Kimberlite
Kimberlite is a type of potassic volcanic rock best known for sometimes containing diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an diamond in 1871 spawned a diamond rush, eventually creating the Big Hole....
and lamproite
Lamproite
Lamproites are ultrapotassic mantle-derived volcanic and subvolcanic rocks. They have low CaO, Al2O3, Na2O, high K2O/Al2O3, a relatively high MgO content and extreme enrichment in incompatible elements....
. They have also been identified in carbonaceous chondrite
Carbonaceous chondrite
Carbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 7 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites...
meteorites as presolar grains
Presolar grains
Presolar grains are isotopically-distinct clusters of material found in the fine-grained matrix of primitive meteorites, such as chondrites, whose differences from the surrounding meteorite suggest that they are older than the solar system...
.
Meteorites
Analysis of SiC grains found in the Murchison carbonaceous chondrite meteorite has revealed anomalous isotopic ratios of carbon and silicon, indicating an origin from outside the solar system. 99% of these SiC grains originate around carbon-rich Asymptotic giant branchAsymptotic Giant Branch
The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass stars. This is a period of stellar evolution undertaken by all low to intermediate mass stars late in their lives....
stars. SiC is commonly found around these stars as deduced from their infrared spectra.
Composition
All applications of silicon carbide today use synthetic material, as the natural material is very scarce. Silicon carbide was first synthesized by Jöns Jacob Berzelius, who is best known for his discovery of siliconSilicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
. Years later, Acheson produced viable minerals that could substitute diamond as an abrasive and cutting material. This was possible as moissanite is one of the hardest substances known, with a hardness below that of diamond
Diamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
and comparable with those of cubic boron nitride
Boron nitride
Boron nitride is a chemical compound with chemical formula BN, consisting of equal numbers of boron and nitrogen atoms. BN is isoelectronic to a similarly structured carbon lattice and thus exists in various crystalline forms...
and boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
. Since naturally occurring moissanite is so rare, lab-grown moissanite is the only commercially viable version of the mineral. More recently, pure synthetic Moissanite has been made from thermal decomposition of the preceramic polymer poly(methylsilyne), requiring no binding matrix (e.g. cobalt metal powder).
Physical properties
The crystalline structure is held together with strong covalent bonding similar to diamonds, that allows moissanite to withstand high pressures up to 52.1 gigapascals. Colours vary widely and are graded in the I-J-K range on the diamond color grading scaleDiamond color
A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color. However, in reality almost no gem-sized natural diamonds are absolutely perfect. The color of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice...
.
Applications
Moissanite has several applications. Since 1998, when the first moissanite reached the jewelry market, it has been regarded as an excellent fine jewel, with optical properties exceeding those of diamond. Because it has its own unique appearance, it can not be truly called a diamond simulantDiamond simulant
The high price of gem-grade diamonds, as well as significant ethical concerns of the diamond trade, have created a large demand for materials with similar gemological characteristics, known as diamond simulants or imitations. Simulants are distinct from synthetic diamond, which unlike simulants is...
. Its ethical production, however, does make it a popular alternative to diamonds. In many developed countries, the use of moissanite in jewelry has been patented; these patents expire in 2015.
Because of its hardness, it is useful for high-pressure experiments (e.g., using diamond anvil cell
Diamond anvil cell
A diamond anvil cell is a device used in scientific experiments. It allows compressing a small piece of material to extreme pressures, which can exceed 3,000,000 atmospheres ....
) competing there with diamond. Large diamonds, used for anvils, are prohibitively expensive. Therefore for large-volume experiments, synthetic moissanite is a more realistic choice. Synthetic moissanite is also interesting for electronic
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
and thermal applications because its thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
is similar to that of diamonds. High power SiC electronic devices are expected to play an enabling and vital role in the design of protection circuits used for motors, actuator
Actuator
An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which...
s, and energy storage or pulse power systems.
External links
- Whatismoissanite.com Journal of Gemmology, 1999, June 9, 1998 : Silicon Carbide Gemstones by Charles Eric Hunter et. al