Mineralpedia Details for Bertrandite

Named for French mineralogist Emile Bertrand. An uncommon mineral that is found in fissures in granite and associated pegmatites, as well as in crystal lined cavities in greisens, and is often found as an common alteration product of beryl, but rarely as a primary mineral. Numerous localities, however pure specimens and large crystals come from localities in France, the Czech Republic, Italy, the United States, Mexico, Brazil, Namibia, South Korea, and Kazakhstan. Minerals associated with Bertrandite include beryl, phenakite, herderite, tourmaline, muscovite, fluorite, and quartz. Bertrandite is pyroelectric and will generate a charge in response to temperature changes.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/bertrandite.pdf

Formula

Be₄Si₂O₇(OH)₂ 

Crystal System

Orthorhombic 

Crystal Habit

Crystalline - Fine, Tabular, Prismatic 

Cleavage

Perfect, Distinct, Distinct 

Luster

Vitreous (Glassy) 

Color

colorless, pale yellow 

Streak

white 

Class

Orthorhombic - Pyramidal 

Fracture

Brittle 

Hardness

6-7 

WebMineral

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Mindat

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Special Info

Phillips Collection

Good eastern US pegmatite representative mineral from this important pegmatite province,

White prismatic Bertrandite crystals to 3mm covering pink Rhodochrosite on Quartz with dark Sphalerite crystals.

Colorless, sharp and well-defined orthorhombic crystals to maybe 0.75mm composing of the entire mass of this specimen.

Colorless tiny and fabulous micro crystals lining the many crevices and vugs of this specimen.