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| Arfvedsonite is
named after the Swedish chemist, Johan A. Arfvedson (1792-1841).
| Discovered
in 1823;
IMA
status: Valid (pre-IMA; Grandfathered) |
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Chemistry
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Chemical
Formula: |
NaNa2[(Fe2+,Mg)4Fe3+]Si8O22(OH)2
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Sodium
Iron Magnesium Silicate Hydroxide |
Molecular
Weight: |
958.89 gm
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Composition: |
Sodium |
7.19 % |
Na |
9.70 % |
Na2O |
|
Iron |
29.12 % |
Fe |
29.97 % |
FeO
/ 8.33 % Fe2O3 |
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Silicon |
23.43 % |
Si |
50.13 % |
SiO2 |
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Hydrogen |
0.21 % |
H |
1.88 % |
H2O |
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Oxygen |
40.04 % |
O |
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|
|
100.00 % |
|
100.00 % |
= TOTAL OXIDE |
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Classification
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Mineral
Classification: |
Silicates
(Germanates)
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Strunz 8th
Ed. ID:
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8/F.08-100
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Nickel-Strunz 10th
Ed. ID:
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9.DE.25
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9 : SILICATES (Germanates)
D : Inosilicates E : Inosilicates with 2-periodic double chains, Si4O11; Clinoamphiboles
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Related
to: |
Amphibole Group, Sodic Clino-Amphibole Subgroup.
Arfvedsonite-Magnesio-Arfvedsonite Series.
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Members
of Group: |
Amphibole Group:
Mg-Mn-Fe-Li Clino-Amphibole Subgroup, Calcic Clino-Amphibole Subgroup,
Sodic Clino-Amphibole Subgroup, Mg-Fe-Mn-Li Ortho-Amphibole Subgroup
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Varieties: |
Anophorite,
Juddite
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Synonyms: |
Arfvedsonite (of Brooke),
Arfwedsonite, Soda-Hornblende
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Crystal
Data
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Crystallography:
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Monoclinic
- Prismatic
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Crystal
Habit:
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Commonly
as elongated prisms, striated and unterminated, to 0.60
m; may be tabular. As prismatic aggregates and radiating
fibrous clusters.
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Twinning:
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Simple
or lamellar twinning
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Physical
Properties
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Cleavage: |
Perfect
on {110}
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Fracture: |
Irregular/Uneven
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Tenacity:
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Brittle
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Moh's
Hardness: |
5.5
- 6.0
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Density:
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3.44 - 3.45 (g/cm3)
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Luminescence:
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None
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Radioactivity:
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Not
Radioactive
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Optical
Properties
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Color: |
Black,
Bluish Gray, deep Green on thin edges |
Transparency: |
Transparent
to Opaque |
Luster: |
Vitreous
(glassy); Silky when fibrous |
Refractive
Index: |
1.652 - 1.708 Biaxial
( - ) |
Birefringence: |
0.009 - 0.014
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Dispersion: |
Strong;
r > v
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Pleochroism: |
Strong,
in blue-greens, yellow-browns, or gray-violets.
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Occurances
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Geological
Setting: |
Common
in alkalic granites and other alkalic plutonic rocks
and pegmatites.
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Common
Associations: |
Nepheline,
Albite, Aegirine, Riebeckite, Katophorite, Magnesio-katophorite,
Quartz.
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Common
Impurities: |
Ti,
Mn, Ca, Al, K, F
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Type
Locality: |
Kangerdluarssuq (Kangerdluarsuk) Firth, Ilimaussaq
complex, Narsaq, Kitaa (West Greenland) Province, Greenland |
Year
Discovered: |
1823
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View
mineral photos: |
Arfvedsonite
Mineral Photos and Locations |
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More
Information
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|
Mindat.org
Webmineral.com
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Arfvedsonite
is a sodium rich Amphibole
Group mineral whose members are important rock forming minerals. It is an uncommon
mineral and gem. Arfvedsonite is mostly glassy black
but can show beautiful chatoyancy with flashes of blue,
green and gold. It is almost always opaque, except in thin
slices, so cabochons are the most common gem form.
The best localities for finding
Arfvedsonite include Mont Saint-Hilaire, Quebec,
Canada; the Ilimaussaq
Intrusion, in Southern Greenland; the agpaitic pegmatites of the Kola Peninsula, Russia and Langesundfjord, Norway.
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