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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