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Sheldrickite crystals – 3mm
Photo by Gilles Haineault
© Gilles Haineault
Sheldrickite crystals
© Doug Merson
NaCa(CO · H
Sheldrickite occurs in a marble xenolith in the nepheline syenite intrusive unit close to a large unit of hornfels. The crystals were found in a cavity between shortite crystals and as flakes in thin seams between crystals of shortite. This mineral assemblage is thought to be a late stage hydrothermal infilling.
Sheldrickite does not display any fluorescence. The specimens were collected in 1991 and only 60 mg are known to exist which makes it a very rare mineral.
PHYSICAL CHARACTERISTICS:
Color is colorless to white.
Luster is vitreous to silky.
Diaphaneity is opaque.
Crystal System is trigonal,
Crystal Habits include aggregates of blocky twinned crystals, radiating
thin flakes and fibrous masses to 2mm.
Cleavage {001} is good.
Fracture is uneven.
Hardness is 3
Specific Gravity is approximately 2.86 g/cm
Streak is white.
Associated Minerals include aegirine, arfvedsonite, calcite, fluorite,
galena, kogarkoite, leucosphenite, microcline, molybdenite, pectolite,
polylithionite, schairerite, sphalerite, thenardite and thermonatrite.
Origin: Named in 1997 in honor of George M. Sheldrick, creator of the
SHELX software, widely used for the refinement of crystal structures.
CLASSIFICATION:
Dana System
# 16a.3.11.1
Strunz Classification
# V/C.06-27
REFERENCES:
CanMin 35:181-187 (1997)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:
MSH
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