Epistolite
Na₄Nb₂Ti(Si₂O₇)₂O₂(OH)₂ · 4H₂O

     Epistolite is moderately rare at MSH. It was originally thought to be murmanite. A new formula for epistolite was recently published in the Canadian Mineralogist, Volume 42, pages 797-806 (2004).

PHYSICAL CHARACTERISTICS:

Color is tan, silvery, pinkish beige and yellow-gray.
Luster is vitreous and pearly to silky on lamellar habit.
Diaphaneity is translucent and opaque on lamellar habit.
Crystal System is triclinic; P1.
Crystal Habits include sharp well-formed platy crystals to 5cm
   and embedded lamellar to micaceous masses.
Cleavage {100} is perfect.
Fracture is uneven.
Hardness is 2 - 3.
Specific Gravity is approximately 2.8 g/cm³.
Streak is white.
Associated Minerals include aegirine, albite, analcime, eudialyte,
   microcline and nenadkevichite.
Distinguishing Features: Crystal habit and color.
Origin: Named in 1897 from the Greek epistole, letter, in allusion
   to its white color and flat, rectangular habit.

CLASSIFICATION:

REFERENCES:
MinRec 21:308 (1990), Dana 8:1176-1177 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

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