Beryl

minerals

schorl

beryllium mineral

aquamarine

Formula: Be3Al2Si6O18
Cyclosilicate (ring silicate)

Varieties

Pure beryl is colourless, but it occurs in many different colours due to impurities. Together, divalent and trivalent iron, Fe2+ and Fe3+ generate the common sea-green color of beryl (R&M 90.2.140).

The blue-green colour of aquamarine is caused by trivalent iron Fe3+ (R&M 90.2.140).
The vivid green of emerald is caused by chromium Cr3+ and vanadium V3+ (R&M 90.2.140).
Goshenite is the colourless, gemmy variety of beryl.
The golden yellow colour of heliodor is caused by divalent iron Fe2+ (R&M 90.2.140).
The pink of morganite is caused by small amounts of divalent manganese Mn2+, and oxidation to Mn3+ causes the deep red of red beryl (R&M 90.2.140).
Red beryl is a gooseberry-red variety of beryl

Properties

Specific gravity: 2.63 to 2.92
Hardness: 7½ to 8
Streak: White
Solubility: Insoluble in hydrochloric, sulphuric and nitric acid
Environments:

Plutonic igneous environments
Pegmatites (typical)
Metamorphic environments

Beryl, although containing the rare element beryllium, Be, is rather common and widely distributed. It usually occurs in granitic rocks, or in pegmatites. All of the colored varieties of beryl except the dark red hue are found in or in association with pegmatites. It is also found in mica schist of regional metamorphic rocks.

In pegmatites, associations include quartz, microcline, albite, muscovite, biotite, members of the columbite-tantalite series, cookeite, tourmaline, lepidolite, topaz and spessartine.
In medium-temperature metamorphic deposits beryl is associated with topaz, cassiterite and ferberite-hübnerite.
in Alpine and hydrothermal veins it is found with quartz and feldspar.

Red beryl is found in topaz rhyolites with topaz, high-temperature quartz and bixbyite (Extra Lapis 7.9).

Localities

At the Kunar Valley, Nuristan, Afghanistan, beryl variety morganite occurs with spodumene variety kunzite, quartz, lepidolite and albite (R&M 90.2.139).

At Tom's quarry, South Australia, beryl occurs intergrown with childrenite, variscite and strontium and iron bearing crandallite (AJM 17.1.28).

At the Sapo mine, Ferruginha, Conselheiro Pena, Minas Gerais, Brazil, beryl occurs in pegmatite associated with quartz, albite and microcline (Min Rec 40.4.288-289).

At the Pederneira claim, São José da Safira, Doce Valley, Minas Gerais, Brazil, beryl variety morganite has been found with elbaite (R&M 90.2.139).

At the Urucum mine, Minas Gerais, Brazil, beryl variety morganite has been found with schorl on albite (R&M 90.2.139).

At Airy Creek, British Columbia, Canada, aquamarine occurs in a granitic pegmatite dyke that cuts high-grade metamorphic gneiss (R&M 85.1.30).

At the Tanco Mine, Bernic Lake, Lac-du-Bonnet area, Manitoba, Canada, a rare miarolitic crystal of cesium-rich, colourless beryl variety goshenite has been found (R&M 90.2.139).

At Lened, Tungsten, Northwest Territories, Canada, emerald occurs in a series of vuggy quartz/carbonate veins within a calc-silicate skarn. The colour is probably due to traces of vanadium (R&M 85.1.28-29).

At the Little Nahanni Pegmatite Group, Tungsten, Northwest Territories, Canada, goshenite occurs within a series of lithium-bearing pegmatites.

At Mountain River, Mackenzie Mountains, Northwest Territories, Canada, emerald occurs in quartz-plagioclase-carbonate veins hosted in shale, siltstone and sandstone. The colour is due to chromium Cr and vanadium V (R&M 84.4.366-367).

At Port Joli, Nova Scotia, Canada, beryl occurs embedded in pegmatite within a biotite granite (R&M 85.1.31).

The Taylor pegmatite, Ontario, Canada, intrudes altered ultramafic rocks, which are the likely source of chromium which causes the green colour of the emerald which is found there (R&M 85.1.28 ).

At Pingwu County, Sichuan, China, beryl is associated with tin and tungsten minerals.

At Erongo, Namibia, schorl pseudomorphs after beryl have been found (KL p220).

At the Shigar valley, Shigar district, Gilgit-Baltistan, Pakistan, beryl variety aquamarine has been found with inclusions and a surface druse of black tourmaline (R&M 90.2.139).

At Dassu, Braldu Valley, Skardu District, Gilgit-Baltistan, Pakistan, beryl variety aquamarine occurs with spessartine, muscovite and feldspar (R&M 90.2.139).

At the Teston village area, Braldu Valley, Skardu District, Gilgit-Baltistan, Pakistan, beryl occurs with albite and muscovite (R&M 94.5.438).

At the Haramosh mountains, Gilgit-Baltistan, Pakistan, beryl variety aquamarine occurs with spessartine on albite and muscovite (R&M 90.2.139).

At Volodarsk-Volynskii, Zhytomyr Oblast, Ukraine, beryl variety heliodor has been found (R&M 90.2.139).

In New York City, USA, beryl crystals are found in pegmatites that cut schist and gneiss, and also frozen in a smoky quartz matrix.

The Consolidated Quarry at Maine, USA, is in a simple granitic pegmatite, enriched in lithium in some zones. These have cavities which contain albite, muscovite and beryl, together with other minerals. The paragenesis for the beryl alteration is
berylberyllonitemoraesitehydroxylherderitefluorapatitegreifensteinite.
Late-stage low-temperature aqueous fluids likely caused partial dissolution of primary beryl resulting in the formation of hydroxylherderite and other secondary beryllium phosphates (R&M 90.3.275).

At Yucca Valley, California, USA, aquamarine occurs in pockets in pegmatite associated with albite variety cleavelandite and smoky quartz (R&M 87.6.502-508).

In the Sierrita Mountains, Arizona, USA, aquamarine occurs in pegmatites embedded in white quartz enclosed by feldspar, with quartz and mica or in contact with biotite (R&M 88.3.222-230).

At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, beryl is common in the core. Associated minerals include pollucite, spodumene and amblygonite-montebrasite. In the intermediate zone most beryl has been replaced by beryllonite, bertrandite, fluorapatite, albite, hydroxylherderite and moraesite. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.505).

At Stoneham, Oxford county, Maine, USA, beryl occurs mostly in solid pegmatites, and only rarely in pockets. When it is in quartz it is aquamarine, but the beryl occurring in feldspar is common beryl (R&M 91.1.28-33).

At the Lost Hope mine, Miami, Karoi district, Mashonaland West, Zimbabwe, euclase pseudomorphs after beryl have been found (KL p220).

Alteration

At high temperature and pressure beryl commonly alters to different secondary minerals, depending on the pH.
At pH 2 to 3 (strongly acid) quartz is the dominant alteration product.
At pH 4 to 5 bertrandite, euclase or phenakite are formed.
Near the neutral pH of 7 bertrandite or bavenite are produced.
At pH of 8 to 9 (alkaline) bavenite, milarite or bityite are produced.
At pH 10 to 11 (strongly alkaline) epididymite or eudidymite are produced.
At high temperature and pressure beryl becomes unstable and breaks down into chrysoberyl, phenakite and quartz (Extra Lapis 7.9-10).

bertrandite, euclase and quartz to beryl and H2O
Be4Si2O7(OH)2 + 8BeAlSiO4(OH) + 14SiO2 ⇌ 4Be3Al2Si6O18 + 5H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

bertrandite and kaolinite to euclase, beryl and H2O
4Be4Si2O7(OH)2 + 7Al2Si2O5(OH)4 ⇌ 10BeAlSiO4(OH) + 2Be3Al2Si6O18 + 13H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

bertrandite, kaolinite and quartz to beryl and H2O
3Be4Si2O7(OH)2 + 4Al2Si2O5(OH)4 + 10SiO2 ⇌ 4Be3Al2Si6O18 + 11H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

beryl to chrysoberyl, phenakite and silica (dry)
Be3Al2Si6O18 to BeAl2O4 + Be2(SiO4) + 5SiO2 (dry)
Increasing temperature and pressure favours the forward reaction. At a pressure of 4 kbar the equilibrium temperatute is 1300 deg C (AM 71.277-300).

beryl and aluminium silicate to chrysoberyl and silica (water saturated)
Be3Al2Si6O18Be + 2Ky to 3BeAl2O4 + 8SiO2 (water saturated)
At high pressure, above 8 kbar, the aluminium silicate phase is kyanite. Increasing temperature and decreasing pressure favours the forward reaction. At a pressure of 16 kbar the equilibrium temperature is about 850oC (AM 71.277-300).

euclase to beryl, chrysoberyl, phenakite and H2O
20BeAlSiO4(OH) to 3Be3Al2Si6O18 + 7BeAl2O4 + 2Be2(SiO4) + 10H2O
Increasing temperature and decreasing pressure favours the forward reaction. At a pressure of 6 kbar the equilibrium temperature is about 500oC, in the absence of impurities which might be incorporated in the beryl (AM 71.277-300).

euclase to phenakite, chrysoberyl, beryl and H2O
20BeAlSiO4(OH) ⇌ 2Be2(SiO4) + 7BeAl2O4 + 3Be3Al2Si6O18 + 10H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

euclase and silica to beryl, chrysoberyl and H2O
4BeAlSiO4(OH) + 2SiO2 to Be3Al2Si6O18 + BeAl2O4 + 2H2O
Increasing temperature and decreasing pressure favours the forward reaction. At a pressure of 8 kbar the equilibrium temperature is about 500oC, in the absnece of impurities which might be incorporated in the beryl (AM 71.277-300).

euclase and quartz to beryl, kaolinite and H2O
6BeAlSiO4(OH) + 8SiO2 ⇌ 2Be3Al2Si6O18 + Al2Si2O5(OH)4 + H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

euclase and quartz to chrysoberyl, beryl and H2O
4BeAlSiO4(OH) + 2SiO2 ⇌ BeAl2O4 + Be3Al2Si6O18 + 2H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

Common impurities: Fe,Mn,Mg,Ca,Cr,Na,Li,Cs,O,H,OH,H2O,K,Rb

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