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| Aenigmatite
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Discovered
in 1865; IMA
status:
Valid (pre-IMA; Grandfathered)
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Chemistry
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Chemical
Formula: |
Na2Fe52+Ti(Si6O18)O2
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Sodium
Iron Titanium Silicate Oxide |
Atomic
Number: |
1,717.59 gm
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Molecular
Weight: |
127.60 gm
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Composition: |
Sodium |
4.99 % |
Na |
6.73 % |
Na2O |
|
Calcium |
0.77 % |
Ca |
1.08 % |
CaO |
|
Magnesium |
0.65 % |
Mg |
1.08 % |
MgO |
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Zirconium |
0.05 % |
Zr |
0.07 % |
ZrO2 |
|
Titanium |
5.85 % |
Ti |
9.77 % |
TiO2 |
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Manganese |
1.28 % |
Mn |
1.65 % |
MnO |
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Aluminum |
1.01 % |
Al |
1.90 % |
Al2O3 |
|
Zinc |
0.04 % |
Zn |
0.05 % |
ZnO |
|
Iron |
29.95 % |
Fe |
35.76 % |
FeO / 3.07 % Fe2O3 |
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Silicon |
18.15 % |
Si |
38.83 % |
SiO2 |
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Oxygen |
37.26 % |
O |
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|
|
|
100.00 % |
|
99.99 % |
= 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.14-20
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Nickel-Strunz 10th
Ed. ID:
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9.DH.40
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9 : SILICATES (Germanates)
D : Inosilicates H : Inosilicates with 4-periodic single chains, Si4O12
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Related
to: |
Aenigmatite Group.
Sapphirine Supergroup.
Aenigmatite-Wilkinsonite
Series.
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Members
of Group: |
Aenigmatite Group:
Aenigmatite, Krinovite, Kuratite, Wilkinsonite
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Varieties: |
None
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Synonyms: |
Cossyrite,
Cosyrite, ICSD 15283, Kölbingite, PDF 46-1473
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Crystal
Data
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Crystallography:
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Triclinic - Pinacoidal
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Crystal
Habit:
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Crystals
poorly developed, prismatic, to 8 cm; as irregular segregations.
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Twinning:
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By
rotation ⊥ (011) or about [010] of the pseudomonoclinic
cell; polysynthetic
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Physical
Properties
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Cleavage: |
Good
on {010}, {100}
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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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3.81 (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: |
Velvet-black;
in thin section, reddish brown to black
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Transparency: |
Translucent
to opaque |
Luster: |
Vitreous
to greasy |
Refractive
Index: |
1.780
- 1.900 Biaxial ( + )
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Birefringence: |
0.090
- 0.100
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Dispersion: |
Very strong; r < v |
Pleochroism: |
X = yellow brown; Y = red-brown;
Z = dark brown to black |
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Occurances
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Geological
Setting: |
A
primary constituent in sodium-rich alkalic volcanics,
pegmatites, and other silica-poor igneous rocks. |
Common
Associations: |
Aegirine,
Augite, Riebeckite, Arfvedsonite, Hedenbergite, Fayalite,
Ilmenite
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Common
Impurities: |
Al,
Mn, Mg, Ca, K, Cl
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Co-type
Localities: |
•
Kangerluarsuk Fjord (Kangerdluarssuq Fjord), Ilímaussaq complex, Narsaq, Kujalleq, Greenland
• Naujakasik (Naajakasik), Tunulliarfik Fjord (Tunugdliarfik), Ilímaussaq complex, Narsaq, Kujalleq, Greenland
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Year
Discovered: |
1865
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View
mineral photos: |
Aenigmatite
Mineral Photos and Locations |
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More
Information
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Mindat.org
Webmineral.com
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Aenigmatite
is a rare inosilicate
mineral containing titanium, that is a member
of the Aenigmatite Group
of minerals that includes Aenigmatite, Krinovite, Kuratite
and Wilkinsonite. Aenigmatite is primarily found in peralkaline
volcanic rocks, pegmatites, and granites as well as silica-poor intrusive
rocks. It was first described and named in 1865 by German
mineralogist Johann Friedrich August Breithaupt
(1791-1873)
from an occurrence in the Ilimaussaq intrusive complex of southwest Greenland.
The name Aenigmatite
is from the Greek word
αίνιγμα
(aenigma), meaning
a riddle, in
allusion to the uncertain chemical composition of the mineral.
Aenigmatite
is typically opaque, velvet-black in color with vitreous
to greasy luster and often associated with bronze-brown
Astrophyllite crystals. Faceted gems are very rare.
Cabochons are somewhat more common but usually collected
for their flashy bronze Astrophyllite crystals and the
secondary black Aenigmatite crystals, if present, are
not even mentioned.
In
addition to the localities listed below, Aenigmatite was also reported from the Kaidun meteorite, possibly a Mars
meterorite, which landed on a Soviet military base near what is now Al-Khuraybah in Yemen
on
December 3, 1980.
Aenigmatite
distribution:
notable studied occurrences include: at Naujakasik,
near the Tunugdliarfik Fjord, and on the Kangerdluarssuk
Plateau, in the Ilímaussaq intrusion; from Narssârssuk;
and elsewhere in Greenland. In the Khibiny and Lovozero
massifs, Kola Peninsula, Russia. At Sandefjord, Norway.
From Cuddua Mida, Sicily, Italy. In the USA, from Granite
Mountain, near Little Rock, Pulaski County, Arkansas,
and Santa Rosa, Sonoma County, California. In Australia,
from Warrumbungle volcano, Nandewar volcano, and the
Mt. Warning complex, New South Wales; and the Peak Range
Province, Queensland. From Logan Point quarry, Dunedin
volcano, New Zealand.
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