Beryl

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Beryl
Beryl09.jpg
Three varieties of beryl (left to right): morganite, aquamarine and emerald
General
Category Cyclosilicate
Formula
(repeating unit)
Be
3
Al
2
Si
6
O
18
Strunz classification 9.CJ.05
Crystal system Hexagonal
Crystal class Dihexagonal dipyramidal (6/mmm)
H-M symbol: (6/m 2/m 2/m)
Space group P6/mcc
Unit cell a = 9.21  Å, c = 9.19 Å; Z = 2
Identification
Formula mass 537.50 g/mol
ColorGreen, blue, yellow, colorless, pink, black and others
Crystal habit Prismatic to tabular crystals; radial, columnar; granular to compact massive
Twinning Rare
Cleavage Imperfect on {0001}
Fracture Conchoidal to irregular
Tenacity Brittle
Mohs scale hardness7.5–8
Luster Vitreous to resinous
Streak White
Diaphaneity Transparent to translucent
Specific gravity Average 2.76
Optical propertiesUniaxial (-)
Refractive index nω = 1.564–1.595
nε = 1.568–1.602
Birefringence δ = 0.0040–0.0070
Pleochroism Weak to distinct
Ultraviolet fluorescence None (some fracture filling materials used to improve emerald's clarity do fluoresce, but the stone itself does not). Morganite has weak violet fluorescence.
References [1] [2] [3] [4] (p112 )

Beryl ( /ˈbɛrəl/ BERR-əl) is a mineral composed of beryllium aluminium cyclosilicate with the chemical formula Be3Al2Si6O18. [5] Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, and red (the rarest). Beryl can also be black in color. It is an ore source of beryllium. [6]

Contents

Main beryl producing countries Beryl.jpg
Main beryl producing countries

Etymology

The word berylMiddle English : beril – is borrowed, via Old French : beryl and Latin : beryllus, from Ancient Greek βήρυλλος bḗryllos, which referred to a 'precious blue-green color-of-sea-water stone'; [1] from Prakrit veruḷiya, veḷuriya 'beryl' (compare the pseudo-Sanskritization वैडूर्य vaiḍūrya 'cat's eye; jewel; lapis lazuli', traditionally explained as '(brought) from (the city of) Vidūra'), [7] which is ultimately of Dravidian origin, maybe from the name of Belur or Velur, a town in Karnataka, southern India. [8] The term was later adopted for the mineral beryl more exclusively.

When the first eyeglasses were constructed in 13th-century Italy, the lenses were made of beryl (or of rock crystal) as glass could not be made clear enough. Consequently, glasses were named Brillen in German [9] (bril in Dutch and briller in Danish).

Deposits

Beryl of various colors is found most commonly in granitic pegmatites, but also occurs in mica schists in the Ural Mountains, and limestone in Colombia. Beryl is often associated with tin and tungsten ore bodies. Beryl is found in Europe in Norway, Austria, Germany, Sweden (especially morganite), Ireland and Russia, as well as Brazil, Colombia, Madagascar, Mozambique, Pakistan, Afghanistan, South Africa, the United States, and Zambia. US beryl locations are in California, Colorado, Connecticut, Georgia, Idaho, Maine, New Hampshire, New Mexico, North Carolina, South Dakota and Utah.

New England's pegmatites have produced some of the largest beryls found, including one massive crystal from the Bumpus Quarry in Albany, Maine with dimensions 5.5 by 1.2 m (18.0 by 3.9 ft) with a mass of around 18 metric tons; it is New Hampshire's state mineral. As of 1999, the world's largest known naturally occurring crystal of any mineral is a crystal of beryl from Malakialina, Madagascar, 18 m (59 ft) long and 3.5 m (11 ft) in diameter, and weighing 380,000 kg (840,000 lb). [10]

Crystal habit and structure

Beryl crystal structure with view down C axis Beryl Crystal Structure.png
Beryl crystal structure with view down C axis

Beryl belongs to the hexagonal crystal system. Normally Beryl forms hexagonal columns but can also occur in massive habits. As a cyclosilicate beryl incorporates rings of silicate tetrahedra of Si
6
O
18
that are arranged in columns along the C axis and as parallel layers perpendicular to the C axis, forming channels along the C axis. [6] These channels permit a variety of ions, neutral atoms, and molecules to be incorporated into the crystal thus disrupting the overall charge of the crystal permitting further substitutions in Aluminium, Silicon, and Beryllium sites in the crystal structure. [6] These impurities give rise to the variety of colors of beryl that can be found. Increasing alkali content within the silicate ring channels causes increases to the refractive indices and birefringence. [11]

Human health impact

Beryl is a beryllium compound that is a known carcinogen with acute toxic effects leading to pneumonitis when inhaled. [12] Care must thus be used when mining, handling, and refining these gems.

Varieties

Aquamarine and maxixe

Aquamarine Beryl-209736.jpg
Aquamarine

Aquamarine (from Latin : aqua marina, "sea water" [13] ) is a blue or cyan variety of beryl. It occurs at most localities which yield ordinary beryl. The gem-gravel placer deposits of Sri Lanka contain aquamarine. Green-yellow beryl, such as that occurring in Brazil, is sometimes called chrysolite aquamarine. [14] The deep blue version of aquamarine is called maxixe. Maxixe is commonly found in the country of Madagascar. Its color fades to white when exposed to sunlight or subjected to heat treatment, though the color returns with irradiation.

Faceted aquamarine Aquamarin cut.jpg
Faceted aquamarine

The pale blue color of aquamarine is attributed to Fe2+. Fe3+ ions produce golden-yellow color, and when both Fe2+ and Fe3+ are present, the color is a darker blue as in maxixe. Decoloration of maxixe by light or heat thus may be due to the charge transfer between Fe3+ and Fe2+. [15] [16] [17] [18] Dark-blue maxixe color can be produced in green, pink or yellow beryl by irradiating it with high-energy particles (gamma rays, neutrons or even X-rays). [19]

In the United States, aquamarines can be found at the summit of Mt. Antero in the Sawatch Range in central Colorado. Aquamarines are also present in the state of Wyoming, aquamarine has been discovered in the Big Horn Mountains, near Powder River Pass. Another location within the United States is the Sawtooth Range near Stanley, Idaho, although the minerals are within a wilderness area which prevents collecting. In Brazil, there are mines in the states of Minas Gerais, Espírito Santo, and Bahia, and minorly in Rio Grande do Norte. The mines of Colombia, Zambia, Madagascar, Malawi, Tanzania and Kenya also produce aquamarine.

The largest aquamarine of gemstone quality ever mined was found in Marambaia, Minas Gerais, Brazil, in 1910. It weighed over 110 kg (243 lb), and its dimensions were 48.5 cm (19 in) long and 42 cm (16+12 in) in diameter. [4] (p110 ) The largest cut aquamarine gem is the Dom Pedro aquamarine, now housed in the Smithsonian Institution's National Museum of Natural History. [20]

The ancient Romans believed that aquamarine would protect against any dangers while travelling at sea, and that it provided energy and cured laziness. [21]

Emerald

Rough emerald on matrix Beryl var. emeraude sur gangue (Muzo Mine Boyaca - Colombie) 15.jpg
Rough emerald on matrix

Emerald is green beryl, colored by around 2% chromium and sometimes vanadium. [15] [22] Most emeralds are highly included, so their brittleness (resistance to breakage) is classified as generally poor.

The modern English word "emerald" comes via Middle English emeraude, imported from modern French via Old French ésmeraude and Medieval Latin esmaraldus, from Latin smaragdus, from Greek σμάραγδος smaragdos meaning ‘green gem’, from Hebrew ברקת bareket (one of the twelve stones in the Hoshen pectoral pendant of the Kohen HaGadol), meaning ‘lightning flash’, referring to ‘emerald’, relating to Akkadian baraqtu, meaning ‘emerald’, and possibly relating to the Sanskrit word मरकत marakata, meaning ‘green’. [23] The Semitic word אזמרגד izmargad, meaning ‘emerald’, is a back-loan, deriving from Greek smaragdos.

Faceted emerald, 1.07ct, Colombia Smaragd-G-EmpireTheWorldOfGems.jpg
Faceted emerald, 1.07ct, Colombia

Emeralds in antiquity were mined by the Egyptians and in what is now Austria, as well as Swat in contemporary Pakistan. [24] A rare type of emerald known as a trapiche emerald is occasionally found in the mines of Colombia. A trapiche emerald exhibits a "star" pattern; it has raylike spokes of dark carbon impurities that give the emerald a six-pointed radial pattern. It is named for the trapiche , a grinding wheel used to process sugarcane in the region. Colombian emeralds are generally the most prized due to their transparency and fire. Some of the rarest emeralds come from the two main emerald belts in the Eastern Ranges of the Colombian Andes: Muzo and Coscuez west of the Altiplano Cundiboyacense, and Chivor and Somondoco to the east. Fine emeralds are also found in other countries, such as Zambia, Brazil, Zimbabwe, Madagascar, Pakistan, India, Afghanistan and Russia. In the US, emeralds can be found in Hiddenite, North Carolina. In 1998, emeralds were discovered in Yukon.

Emerald is a rare and valuable gemstone and, as such, it has provided the incentive for developing synthetic emeralds. Both hydrothermal [25] and flux-growth synthetics have been produced. The first commercially successful emerald synthesis process was that of Carroll Chatham. [26] The other large producer of flux emeralds was Pierre Gilson Sr., which has been on the market since 1964. Gilson's emeralds are usually grown on natural colorless beryl seeds which become coated on both sides. Growth occurs at the rate of 1 millimetre (0.039 in) per month, a typical seven-month growth run producing emerald crystals of 7 mm of thickness. [27] The green color of emeralds is widely attributed to presence of Cr3+ ions. [16] [17] [18] Intensely green beryls from Brazil, Zimbabwe and elsewhere in which the color is attributed to vanadium have also been sold and certified as emeralds. [28] [29] [30]

Golden beryl and heliodor

Faceted golden beryl, 48.75 ct, Brazil Heliodor-G-EmpireTheWorldOfGems.jpg
Faceted golden beryl, 48.75 ct, Brazil

Golden beryl can range in colors from pale yellow to a brilliant gold. Unlike emerald, golden beryl generally has very few flaws. The term "golden beryl" is sometimes synonymous with heliodor (from Greek hēlios – ἥλιος "sun" + dōron – δῶρον "gift") but golden beryl refers to pure yellow or golden yellow shades, while heliodor refers to the greenish-yellow shades. The golden yellow color is attributed to Fe3+ ions. [15] [16] Both golden beryl and heliodor are used as gems. Probably the largest cut golden beryl is the flawless 2054-carat stone on display in the Hall of Gems, Washington, D.C., United States. [31]

Goshenite

Goshenite Goshenite.jpg
Goshenite
Faceted goshenite, 1.88 ct, Brazil Goshenit-G-EmpireTheWorldOfGems.jpg
Faceted goshenite, 1.88 ct, Brazil

Colorless beryl is called goshenite. The name originates from Goshen, Massachusetts, where it was originally discovered. In the past, goshenite was used for manufacturing eyeglasses and lenses owing to its transparency. Nowadays, it is most commonly used for gemstone purposes. [32] [33]

The gem value of goshenite is relatively low. However, goshenite can be colored yellow, green, pink, blue and in intermediate colors by irradiating it with high-energy particles. The resulting color depends on the content of Ca, Sc, Ti, V, Fe, and Co impurities. [16]

Morganite

Morganite Beryl-Quartz-morganite brazil1.jpg
Morganite
Faceted morganite, 2.01 ct, Brazil Morganit-G-EmpireTheWorldOfGems.jpg
Faceted morganite, 2.01 ct, Brazil

Morganite, also known as "pink beryl", "rose beryl", "pink emerald" (which is not a legal term according to the new Federal Trade Commission Guidelines and Regulations), and "cesian (or caesian) beryl", is a rare light pink to rose-colored gem-quality variety of beryl. Orange/yellow varieties of morganite can also be found, and color banding is common. It can be routinely heat treated to remove patches of yellow and is occasionally treated by irradiation to improve its color. The pink color of morganite is attributed to Mn2+ ions. [15]

Pink beryl of fine color and good sizes was first discovered on an island off the coast of Madagascar in 1910. [34] It was also known, with other gemstone minerals, such as tourmaline and kunzite, at Pala, California. In December 1910, the New York Academy of Sciences named the pink variety of beryl "morganite" after financier J. P. Morgan. [34]

On October 7, 1989, one of the largest gem morganite specimens ever uncovered, eventually called "The Rose of Maine", was found at the Bennett Quarry in Buckfield, Maine, US. [35] The crystal, originally somewhat orange in hue, was 23 cm (9 in) long and about 30 cm (12 in) across, and weighed (along with its matrix) just over 50 pounds (23 kg). [36]

Red beryl

Red beryl Beryl-235618.jpg
Red beryl

Red beryl (formerly known as "bixbite" and marketed as "red emerald" or "scarlet emerald" but note that both latter terms involving "Emerald" terminology are now prohibited in the United States under Federal Trade Commission Regulations) [37] is a red variety of beryl. It was first described in 1904 for an occurrence, its type locality, at Maynard's Claim (Pismire Knolls), Thomas Range, Juab County, Utah. [38] [39] The old synonym "bixbite" is deprecated from the CIBJO, because of the risk of confusion with the mineral bixbyite (both were named after the mineralogist Maynard Bixby). [40] The dark red color is attributed to Mn3+ ions. [15]

Faceted red beryl, 0.56 ct, Utah US RedBeryl-G-EmpireTheWorldOfGems.jpg
Faceted red beryl, 0.56 ct, Utah US

Red beryl is very rare and has been reported only from a handful of locations: Wah Wah Mountains, Beaver County, Utah; Paramount Canyon and Round Mountain, Sierra County, New Mexico, although the latter locality does not often produce gem grade stones; [38] and Juab County, Utah. The greatest concentration of gem-grade red beryl comes from the Ruby-Violet Claim in the Wah Wah Mountains of mid-western Utah, discovered in 1958 by Lamar Hodges, of Fillmore, Utah, while he was prospecting for uranium. [41] Red beryl has been known to be confused with pezzottaite, a caesium analog of beryl, that has been found in Madagascar and more recently Afghanistan; cut gems of the two varieties can be distinguished from their difference in refractive index, and rough crystals can be easily distinguished by differing crystal systems (pezzottaite trigonal, red beryl hexagonal). Synthetic red beryl is also produced. [42] Like emerald and unlike most other varieties of beryl, red beryl is usually highly included.

While gem beryls are ordinarily found in pegmatites and certain metamorphic stones, red beryl occurs in topaz-bearing rhyolites. [43] It is formed by crystallizing under low pressure and high temperature from a pneumatolytic phase along fractures or within near-surface miarolitic cavities of the rhyolite. Associated minerals include bixbyite, quartz, orthoclase, topaz, spessartine, pseudobrookite and hematite. [39]

See also

Related Research Articles

Amethyst Mineral, quartz variety

Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος amethystos from α- a-, "not" and μεθύσκω methysko / μεθώ metho, "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. The ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxication.

Emerald Green gemstone, a beryl variety

Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and/or sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor. Emerald is a cyclosilicate.

Gemstone Piece of mineral crystal used to make jewelry

A gemstone is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks and occasionally organic materials that are not minerals are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone.

Sapphire Gem variety of corundum

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies not sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.

Topaz Silicate mineral

Topaz ( TOH-paz) is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F, OH)2. It is used as a gemstone in jewelry and other adornments. Topaz in its natural state is a golden brown to yellow. A variety of impurities and treatments may make topaz wine red, pale gray, reddish-orange, pale green, pink, or opaque.

Tourmaline Cyclosilicate mineral group

Tourmaline is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a semi-precious stone. This gemstone can be found in a wide variety of colors.

Garnet Mineral, semi-precious stone

Garnets are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.

Ruby Variety of corundum, mineral, gemstone

A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, together with amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.

Chrysoberyl Mineral or gemstone of beryllium aluminate

The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula BeAl2O4. The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones, although they both contain beryllium. Chrysoberyl is the third-hardest frequently encountered natural gemstone and lies at 8.5 on the Mohs scale of mineral hardness, between corundum (9) and topaz (8).

Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin lux, meaning "light", and generally implies radiance, gloss, or brilliance.

Pleochroism Optical phenomenon

Pleochroism is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light.

Hiddenite

Hiddenite is a pale-to-emerald green variety of spodumene that is sometimes used as a gemstone.

Cordierite

Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: (Mg,Fe)2Al3(Si5AlO18) to (Fe,Mg)2Al3(Si5AlO18). A high-temperature polymorph exists, indialite, which is isostructural with beryl and has a random distribution of Al in the (Si,Al)6O18 rings.

Priestly breastplate Jewish ritual object worn by the High Priest

The priestly breastplate was a sacred breastplate worn by the High Priest of the Israelites, according to the Book of Exodus. In the biblical account, the breastplate is sometimes termed the breastplate of judgment, because the Urim and Thummim were placed within it. These stones were, at times, used to determine God's will in a particular situation. Using these stones did not always determine God's will

Pezzottaite Mineral species

Pezzottaite, marketed under the name raspberyl or raspberry beryl, is a mineral species first recognized by the International Mineralogical Association in September 2003. Pezzottaite is a caesium analogue of beryl, a silicate of caesium, beryllium, lithium and aluminium, with the chemical formula Cs(Be2Li)Al2Si6O18. Named after Italian geologist and mineralogist Federico Pezzotta, pezzottaite was first thought to be either red beryl or a new variety of beryl ("caesium beryl"); unlike actual beryl, however, pezzottaite contains lithium and crystallizes in the trigonal crystal system rather than the hexagonal system.

Demantoid

Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals. Andradite is a calcium- and iron-rich garnet. The chemical formula is Ca3Fe2(SiO4)3 with chromium substitution as the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone.

The gemstone irradiation is a process in which a gemstone is artificially irradiated in order to enhance its optical properties. High levels of ionizing radiation can change the atomic structure of the gemstone's crystal lattice, which in turn alters the optical properties within it. As a result, the gemstone's color may be significantly altered or the visibility of its inclusions may be lessened. The process, widely practised in jewelry industry, is done in either a nuclear reactor for neutron bombardment, a particle accelerator for electron bombardment, or a gamma ray facility using the radioactive isotope cobalt-60. Irradiation has enabled the creation of gemstone colors that do not exist or are extremely rare in nature.

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Further reading