(Na,Ca0.50.33(Fe3+,Al)(Si,Al)10(OH) · nH
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; 2/
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/cm
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
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