Elpidite – Saint-Hilaire

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Elpidite crystals - click for larger pic
Elpidite spray of crystals
Photo by Violet Anderson
© Royal Ontario Museum

Elpidite crystals - click for larger pic
Elpidite crystals
© Doug Merson

NaZrSi₁₅ · 3H

Elpidite is moderately rare at MSH, but is sometimes found in relatively large amounts. It is sometimes found as a pseudomorph of sérandite crystals usually coated by a very fine dark green powdery chlorite-group mineral.

PHYSICAL CHARACTERISTICS:

Color is tan, greenish gray to white or colorless.
Luster is vitreous to earthy or silky.
Diaphaneity: the crystals are opaque and rarely translucent.
Crystal System is orthorhombic; Pbm2.
Crystal Habits include sharp, terminated short prismatic crystals; as
elongated needle-like prisms forming attractive sprays.
Cleavage {110} is good.
Fracture is splintery to uneven.
Hardness is 5.
Specific Gravity is approximately 2.6 g/cm
Streak is white.
Associated Minerals include aegirine, albite, bastnäsite, calcite,
chlorite group, epididymite, fluorapatite, natrolite, pyrochlore,
rutile and siderite.
Distinguishing Features include the crystal habit.
Origin: From the Greek elpidos, hope, alluding to the expectancy of
finding other interesting minerals at the discovery locality of Narsarsuk,
Greenland in 1894.

CLASSIFICATION:

Dana System
# 72.5.4.2

Strunz Classification
# VIII/F.23-10

REFERENCES:
MinRec 21:306-307 (1990), Dana 8:1543-1544 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

MSH
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