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Eudidymite twin
L. Horváth specimen
Photo by Violet Anderson
© Royal Ontario Museum
Eudidymite crystals
© Gilles Haineault
Eudidymite crystals
© Modris Baum
NaBeSi(OH)
Eudidymite is relatively rare at Mont Saint-Hilaire. It is the monoclinic dimorph of epididymite.
PHYSICAL CHARACTERISTICS:
Color is usually colorless to white, rarely pale pink.
Luster is vitreous to silky.
Diaphaneity is transparent to translucent.
Crystal System is monoclinic; 2/
Crystal Habits include thin tabular euhedral crystals, the twinned
crystals sometimes form attractive stellate groups ressembling
the epididymite trillings.
Cleavage {001} is perfect and {100} is distinct.
Fracture is uneven.
Hardness is 6 – 7.
Specific Gravity is approximately 2.55 g/cm
Streak is white.
Associated Minerals include aegirine, analcime, catapleiite,
microcline, natrolite and rhodochrosite.
Distinguishing Features: Crystal habit (twinning).
Origin: Named in 1887 from the Greek eu, well, plus didymos, twin,
alluding to its characteristic occurrence as twinned crystals.
CLASSIFICATION:
Dana System
# 66.3.1.3
Strunz Classification
# VIII/G.04-10
REFERENCES:
MinRec 21:309 (1990), Dana 8:1370-1371 (1997)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:
MSH
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Eudidymite crystals
© Doug Merson
Eudidymite crystals
© Modris Baum
Eudidymite crystals
© Stephan Wolfsried
Eudidymite crystals
© Doug Merson