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Minerals - Bertrandite | TerraCollect

Mineral - Bertrandite

BertranditeBe₄(Si₂O₇)(OH)₂

Chemical Properties

Mineral Class

Silicates

Toxicity

none

Formula

Be₄(Si₂O₇)(OH)₂

Unit Cell

a=8.72 b=15.27 c=4.57 Z=4

Physical Properties

Hardness

6 - 7

Streak

white

Density

Normal (2-3,5)

Optical Properties

Color

whitecolorless

Birefringence

0.023

Luster

Vitreous,

Pearly

Transparency

translucent,

transparent

Pleochroism

Geomineralogical Properties

Crystal System

orthorhombic

Composition

Elements

Mass

SiO₂

49.26

Al₂O₃

0.01

Fe₂O₃

1.40

BeO

42.00

H₂O

6.90

France (Dana 1892)

Karten-Ebenen

Geologische KarteSatelliten Karte

Cleavage

Perfect after {001}, distinct after {100}, {010}, {110}

Fracture

uneven

Tenacity

Brittle

Point Group

orthorhombic-pyramidal - mm2

Space Group

Cmc21 (36)

Habit

blocky, acicular, prismatic, radial, tabular

Formation

Secondary, through the hydrothermal alteration of Beryl in granitic, miarolitic cavities

Paragenesis

Twinning

After {011} or {021}, as heart-shaped, V-shaped or Y-shaped twins

Rarity

Rather rare

Synonyms

Bertrandite, Hessenbergite