Sanidine
(K,Na)AlSi3O8

     Sanidine, a member of the feldspar group, is moderately rare at MSH.
It is of little mineralogical interest and hard to distinguish from the other members of the feldspar group.

PHYSICAL CHARACTERISTICS:

Color is usually colorless, white or pale pink.
Luster is vitreous.
Diaphaneity is transparent to translucent.
Crystal System is monoclinic; C2/m.
Crystal Habits include sharp blocky wedge-shaped crystals to 0.5mm.
Cleavage {001} and {010} are perfect.
Fracture is uneven to conchoidal.
Hardness is 6 - 6.5
Specific Gravity is approximately 2.6 g/cm3.
Streak is white.
Associated Minerals include microcline.
Distinguishing Features: Crystal habit and luster.
Origin: Named in 1808 from the Greek sanida, a board, alluding to its
   typical tabular habit.

CLASSIFICATION:

Dana System
# 76.1.1.2

Strunz Classification
# VIII/J.26-20

REFERENCES:
MinRec 21:334 (1990), Dana 8:1602-1603 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

MSH
¤¤¤

PE
--

AP
--

MX
¤¤

SS
--

MC
--

HF
--

BR
--

SX
--

FR
--

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