Euclase

beryllium

bertrandite

Formula: BeAlSiO4(OH)
Nesosilicate (insular SiO4 groups), beryllium mineral
Specific gravity: 2.99 to 3.10
Hardness: 7½
Streak: White
Colour: Colourless, white, pale green to deep yellowish green, greenish blue, pale blue to deep blue
Solubility: Insoluble in acids
Environments:

Pegmatites
Metamorphic environments
Hydrothermal environments

Euclase is a low-temperature hydrothermal mineral in granite pegmatites and Alpine veins. It is also found in chlorite schist and phyllite, and as a detrital mineral (Dana). In pegmatites it is a product of decomposition of beryl (HOM). Associated minerals include feldspar, quartz, topaz, beryl, mica, calcite, ankerite and chlorite (HOM).

The type locality is Ouro Preto, Minas Gerais, Brazil.

Alteration

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 and kaolinite to euclase, quartz and H2O
Be4Si2O7(OH)2 + 2Al2Si2O5(OH)4 ⇌ 4BeAlSiO4(OH) + 2SiO2 + 3H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

chrysoberyl, bertrandite and kaolinite to euclase and H2O
2BeAl2O4 + 2Be4Si2O7(OH)2 + 3Al2Si2O5(OH)4 ⇌ 10BeAlSiO4(OH) + 3H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

euclase to bertrandite, chrysoberyl, quartz and H2O
8BeAlSiO4(OH) ⇌ Be4Si2O7(OH)2 + 4BeAl2O4 + 6SiO2 + 3H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

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 kaolinite to chrysoberyl, quartz and H2O
2BeAlSiO4(OH) + Al2Si2O5(OH)4 ⇌ 2BeAl2O4 + 4SiO2 + 3H2O
Increasing temperature favours the forward reaction (AM 63.664-676).

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: Zn,F,Ca,Mg,Fe,Na

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