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Nontronite
(Na,Ca0.5)0.33(Fe3+,Al)2(Si,Al)4O10(OH)2 · nH2O

     Nontronite occurs rarely at MSH.

PHYSICAL CHARACTERISTICS:

Color varies from dark brown to black, golden yellow, red and brown.
Luster is resinous to waxy to earthy.
Diaphaneity is translucent to opaque.
Crystal System is monoclinic; C2/m.
Crystal Habits include balls and flakes in irregular patches.
Cleavage {001} is perfect.
Fracture is conchoidal.
Hardness is 1 - 2.
Specific Gravity is approximately 2.2 g/cm3.
Streak is white.
Associated Minerals include aegirine, analcime, microcline and
   natrolite.
Distinguishing Features: Crystal habits.
Origin: Named in 1827 after its discovery locality, near the village of
   Saint-Pardaux, Nontron, France.

CLASSIFICATION:

Dana System
# 71.3.1a.3

Strunz Classification
# VIII/H.19-40

REFERENCES:
Dana 8:1485-1486 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

MSH
¤¤¤

PE
¤¤

AP
¤¤

MX
--

SS
--

MC
--

HF
--

BR
--

SX
--

FR
--

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