Mangan-neptunite – Saint-Hilaire

KNaLi(Mn,Fe⁺²Ti₁₂Si₁₈₂₄

Splendid deep red prisms of mangan-neptunite up to 5 cm have been found at Mont Saint-Hilaire. Color zoning is often present and is dependent on the Mn:Fe ratio. Some of the crystals are etched, cavernous and crumbly.

Mangan-neptunite crystals - click for larger pic
Mangan-neptunite crystal associated with sérandite and catapleiite – 2,5 x 2,5 cm
© Gilles Haineault

PHYSICAL CHARACTERISTICS:

Color varies from reddish brown to orange and very deep carmine-red
to black.
Luster is vitreous to waxy to dull on external surfaces and resinous
on fractured internal surfaces.
Diaphaneity is transparent to translucent in the smaller crystals,
while the larger one tend to be opaque.
Crystal System is monoclinic; Cc
Crystal Habits include well formed, elongated, commonly twinned,
monoclinic prisms and equant pseudorhombohedra. Rarely in breccia
as sharp, twinned tabular crystals.
Cleavage {110} is perfect.
Fracture conchoidal.
Hardness varies from 5 to 6.
Specific Gravity is approximately 3.2g/cm
Streak is reddish-brown.
Associated Minerals include aegirine, albite, amphibole group,
analcime, apophyllite group, astrophyllite, calcite, catapleiite,
fluoroapatite, microcline, natrolite, nenadkevichite, polylithionite,
raite, rhodochrosite and sérandite.
Distinguishing Features: Crystal habit, etching on some crystals.
Origin: Named in 1923 for its composition: manganese and its
relationship with neptunite.

CLASSIFICATION:

Dana System
# 70.4.1.2

Strunz Classification
# VIII/F.37-20

REFERENCES:
MinRec 21:321 (1990), Dana 8:1402 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

MSH
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