Mineralpedia Details for Eudidymite

Named after a combination of the Greek words eu, used as a prefix to mean “fair” or “good,” and didymos, meaning “twinned,” in reference to the mineral’s common appearance as twinned crystals. Eudidymite is an uncommon mineral that occurs in Norway, England, the Czech Republic, Russia, Canada, Malawi, and others as a late-stage mineral in alkaline nepheline syenite pegmatites. Associated minerals include albite, neptunite, aegirine, elpidite, natrolite, analcime, fluorite, and quartz.

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

Formula

Na₂Be₂Si₆O₁₅·H₂O 

Crystal System

Monoclinic 

Crystal Habit

Twinning Common, Tabular 

Cleavage

Good, Good, None 

Luster

Vitreous (Glassy) 

Color

blue, colorless, violet, gray, yellow 

Streak

white 

Class

Monoclinic - Prismatic 

Fracture

Brittle 

Hardness

6 

WebMineral

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Mindat

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A 3cm fan-like, platy crystal group.