Red beryl

Red beryl, formerly known as bixbite and marketed as red emerald or scarlet emerald, is an extremely rare variety of beryl as well as one of the rarest minerals on Earth.  The gem gets its red color from manganese ions incorporated within the beryl crystal structure. The color of red beryl is stable up to 1,000 °C (1,830 °F). Red beryl can come in various tints like strawberry, bright ruby, cherry, and orange.

The largest crystals of red beryl are about 2 cm (0.79 in) wide and 5 cm (2.0 in) long. However, most crystals are under 1 cm (0.39 in) long. Recently, the red variety of pezzottaite has been sold in markets as red beryl by some sellers.

Red beryl

General

Category Cyclosilicate beryl

Formula Be3Al2Si6O18 with a mix of Mn3+ ions

Crystal system Hexagonal

Space group P6/mcc

Identification

Color Dark red

Twinning Extremely rare

Cleavage Indistinct

Fracture Conchoidal

Mohs scale hardness 7.5–8

Luster Vitreous

Streak white

Specific gravity 2.66–2.87

Optical properties Uniaxial (−)

Refractive index 1.560–1.577

Birefringence δ = 0.0040–0.0080

Dispersion 0.014

Ultraviolet fluorescence None

Etymology and history

Bixbite was the original name given by Alfred Eppler in 1912 to the red beryl discovered by Maynard Bixby (1853–1935). However, this first name was rejected by the CIBJO due to the risk of confusion with the mineral bixbyite, also named after Bixby, and is no longer to be used. 

Maynard Bixby, an American prospector and claim owner, first discovered small, opaque, and intensely red beryl crystals in "Topaz Cave" (Maynard Topaz Mine) in Juab County, Utah, USA, in 1897. Gem-quality red beryl, however, was not discovered until 1958 in the Wah Wah Mountains in Beaver County, Utah, USA.

History

Red beryl was discovered in 1904 by Maynard Bixby in the Wah Wah mountains in Utah. In 1912 the gem was named bixbite by Alfred Eppler after Maynard Bixby. The old synonym "bixbite" is deprecated, since it can cause confusion with the mineral bixbyite.

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. This claim was bought by Denise Knoeller as part of Red Emerald Inc. in 2020.

Characteristics

The dark red color of red beryl is attributed to Mn3+ ions. Red beryl rough crystals can be easily distinguished by hexagonal crystal systems. This gem 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. Red beryl is similar to emerald and dissimilar to other beryls in that it has inclusions like feathers and fractures. Some mineral inclusions include quartz, feldspar, hematite, and bixbyite.

Chemistry

The hexagonal crystal system found in beryls are formed of AlO6 octahedra, as well as BeO4 and SiO4 tetrahedra. The hexagonal channels of red beryl are primarily unoccupied and no detectable water has been found within Red beryl gets its color from natural chemical doping, whereby Mn3+O6 replaces AlO6 at certain positions. The deep color Mn3+O6 may be in part explained by the Jahn-Teller effect on spin disallowed transitions.

Color

The rare red color of red beryl is caused by Mn 2+, which replaces the Al atom in the crystal lattice. The best color is a rich red ("stoplight") with a hint of blue. Colors vary between orange-red, pink, reddish-violet, and dark red, with many intermediate shades.

Rarity

Red beryl is very rare and has been reported only from a handful of locations: Wah Wah Mountains, Paramount Canyon, Round Mountain and Juab County, all in the south-western United States. The narrow geographic range suggests that the specific conditions needed for its formation do not occur frequently. This gem is a thousand times rarer than gold.

The Utah Geological Survey estimated that one red beryl is found for every 150,000 diamonds. According to Gemmological Association of Great Britain a 2 carat red beryl is as rare as a 40 carat diamond.

Red beryl is valued roughly the same price or higher than emerald despite being a hundred times rarer. Its rarity has made it less popular but red beryl crystals that are over 1 carat can sell for US$20,000.  In 2008, one carat could sell for US$5000 or more.

Limited geographical occurrence means that the Red Emerald Inc controlled world production of natural red beryl as of 2021.

Formation

While gem beryls are ordinarily found in pegmatites and certain metamorphic rock, red beryl forms in topaz-bearing rhyolites. 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. Synthetic red beryl is produced using hydrothermal process similar to that used for emeralds, however cobalt and manganese are used as dopants to produce a dark red gem.

Depositology and associated minerals

Gemstone beryls are found mainly in pegmatites and metamorphic rocks. They form under low pressure and high temperature in the cavities of rhyolites.

Associated minerals: in rhyolite with bixbyite, hematite, garnets, pseudobrookite, quartz, sanidine, spessartine, topaz.

Deposits producing remarkable specimens

This variety of beryl remains rare. Three occurrences are known in the United States:

Thomas Range, Juab County, Utah (topotype);

Wah Wah Mountains, Beaver County, Utah. The largest concentration of gem-quality red beryl is found at the Violet Claim in the Wah Wah Mountains, west-central Utah, discovered in 1958 by Lamar Hodges of Fillmore while prospecting for uranium ;

Round Mountain, Sierra County, New Mexico.

Use as a gemstone

Red beryl is almost exclusively used to make gemstones, but due to its rarity it is often replaced by irradiated or fired beryl varieties or synthetics.

Red beryl is the rarest of beryls. Most faceted stones weigh less than 1 carat and contain inclusions ranging from opaque " bubble gum " quality to pink. However, "bubble gum" is also used as a color name for pink, regardless of clarity. The largest crystal found to date measured 1.4 × 3.4 cm and weighed 54 ct. The largest faceted red beryl (not pure) weighs 8 ct. The usual size of good, faceted stones is only 0.15 ct.

Faceted, pure stones with the coveted "stoplight" red are highly sought after. If they weigh over 1 ct, they are extremely rare and command a correspondingly high price.

According to the Geological Survey of Utah, red beryl is so rare that only about one red beryl is mined for every 150,000 gem-quality diamonds. 

Differentiation from Pezzottait

n 2002, a pink mineral was discovered in Madagascar, initially thought to be a less valuable variety of "red beryl" and named pezzottaite. Since 2003, however, pezzottaite has been recognized as a separate mineral, which, although related to the other minerals of the beryl group, differs so much in structure that it is not isostructural with them. 

Red beryl has hexagonal crystals with six equal sides, capped by flat ends. Pezzottaite has trigonal crystals with pyramid-like ends. Pezzottaite crystals are typically larger than red beryl crystals. The parent rock (matrix) of red beryl is white or gray rhyolite. Pezzottaite crystals sit on gray granite.

Typically, red beryls are not eye-clean if the stone/crystal weighs more than 1/10 of a ct. They typically have inclusions, internal cracks, rhyolite haze, and/or black spots. Pezzottaite typically exhibits blisters and/or cracks. Red beryl has a refractive index of 1.567 to 1.580, while pezzotaite has a refractive index of 1.601 to 1.620.

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