Stillwellite-(Ce)
(Ce,La,Th,Ca)BSiO₅

     Stillwellite-(Ce) is a rare mineral at MSH. It is difficult to recognize because of its crystal size and color.

PHYSICAL CHARACTERISTICS:

Color is usually pale pink.
Luster is vitreous to dull.
Diaphaneity is transparent to opaque.
Crystal System is hexagonal; P3₁.
Crystal Habits include sharp hexagonal crystals terminated by
   rhombohedra.
Cleavage not known.
Fracture is conchoidal.
Hardness is 5.5 - 6.5
Specific Gravity is approximately 4.65 g/cm³.
Streak is white.
Associated Minerals include aegirine, albite, amphibole group,
   ancylite, apophyllite series, calcite, microcline, rinkite (mosandrite),
   steacyite and titanite.
Distinguishing Features: Crystal habit, color and luster.
Origin: Named in 1955 after Frank Leslie Stillwell (1888-1963),
   Austrian ore mineralogist.

CLASSIFICATION:

REFERENCES:
MinRec 21:341 (1990), Dana 8:1129 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

Legend