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| Tephroite
was named in 1823 by Johann Friedrich August Breithaupt from Greek word
tephros meaning
ash-colored, alluding to the usual gray color of the
mineral.
| Discovered
in 1823; IMA
status:
Valid (pre-IMA; Grandfathered) |
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Chemistry
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Chemical
Formula: |
Mn2+2SiO4
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Manganese
Silicate |
Molecular
Weight: |
201.96 gm
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Composition: |
Manganese |
54.41 % |
Mn |
70.25 % |
MnO |
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Silicon |
13.91 % |
Si |
29.75 % |
SiO2 |
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Oxygen |
31.69 % |
O |
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|
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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/A.04-30
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Nickel-Strunz 10th
Ed. ID:
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9.AC.05
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9 : SILICATES (Germanates)
A : Nesosilicates C : Nesosilicates without additional anions; cations in octahedral [6] coordination
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Related
to: |
Olivine Group. Fayalite-Tephroite Series.
Forsterite-Tephroite Series. The Mn2+ analogue of Fayalite, Forsterite, and Calcio-Olivine.
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Members
of Group: |
Olivine
Group: Calcio-olivine, Fayalite, Forsterite, Claucochroite,
Kirschsteinite, Laihunite, Liebenbergite, Monticellite,
Olivine, Roepperite, (of Brush), Tephroite
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Varieties: |
None
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Synonyms: |
Mangan-Peridot,
ICSD 100433, PDF 35-748
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Crystal
Data
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Crystallography:
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Orthorhombic - Dipyramidal
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Crystal
Habit:
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Crystals
typically short, prismatic, to 4 cm, or anhedral, equidimensional.
Commonly in disseminated grains, compact, or massive.
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Twinning:
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{011},
not common
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Physical
Properties
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Cleavage: |
Distinct
on {010}, imperfect on {001}
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Fracture: |
Uneven
to conchoidal
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Tenacity:
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Brittle
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Moh's
Hardness: |
6.0
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Density:
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3.87
- 4.12 (g/cm3)
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Luminescence:
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None.
Often associated with fluorescent minerals such as Calcite
and Willemite.
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Radioactivity:
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Not
Radioactive
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Optical
Properties
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Color: |
Olive-green,
bluish green, gray, flesh-red, reddish brown; pale green
in thin section, may be colorless.
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Transparency: |
Transparent
to translucent |
Luster: |
Vitreous
to greasy |
Refractive
Index: |
1.759
- 1.860 Biaxial ( - )
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Birefringence: |
0.101
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Dispersion: |
r > v |
Pleochroism: |
None or weak; X
= brownish red; Y
= reddish; Z
= greenish blue |
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Occurances
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Geological
Setting: |
In
Fe-Mn ore deposits, related skarns, and metamorphosed
manganese-rich sediments.
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Common
Associations: |
Zincite,
Willemite, Franklinite, Rhodonite, Jacobsite, Diopside,
Gageite, Bustamite, Manganocalcite, Glaucochroite, Calcite,
Banalsite, Alleghanyite
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Common
Impurities: |
Fe,
Zn, Ca, Mg
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Type
Locality: |
Sterling Mine, Sterling Hill, Ogdensburg, Franklin Mining District, Sussex County, New Jersey, USA
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Year
Discovered: |
1823
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View
mineral photos: |
Tephroite
Mineral Photos and Locations |
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More
Information
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|
Mindat.org
Webmineral.com
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Tephroite
is a manganese silicate mineral that is a member of
the Olivine Group of minerals that includes Fayalite,
Forsterite,
Olivine
and Tephroite.
Tephroite forms a series with Fayalite.
Tephroite is the manganese rich member of the series and Fayalite is the iron rich member.
Tephroite is a contact metamorphic and hydrothermal replacement mineral. It is commonly ash gray but also is found in
colors of olive-green, greenish-blue, pink or brown.
The type locality for Tephroite is the famous Sterling Mine, Sterling Hill, Ogdensburg, Franklin Mining District, Sussex County, New Jersey, USA.
The Sterling Mine and nearby Franklin Mines are well
known for their mineral abundance and diversity. In the area of the Franklin and Sterling Hill mines, 357 types of
minerals are known to occur; these make up approximately 10% of the
minerals known to science. Thirty-five of these minerals have not been
found anywhere else. Ninety-one of the minerals are fluorescent. Tephroite is
not a fluorescent mineral but is ofter found associated
with fluorescent minerals such as Bustamite,
Calcite,
Willemite
and Zincite.
Tephroite
was named in 1823 by Johann Friedrich August Breithaupt from Greek word
tephros meaning
ash-colored, alluding to the usual gray color of the
mineral.
Locations
for Tephroite: In the USA, from Franklin and Sterling
Hill, Ogdensburg, Sussex County, New Jersey; at Bald
Knob, near Sparta, Alleghany County, North Carolina;
and in the Sunnyside mine, San Juan County, Colorado.
From Buritirama, Piaui, Brazil. In the Harstigen mine,
near Persberg; at Långban, Värmland; and
in the Sjö mine, near Grythyttan, Örebro,
Sweden. From the Benallt mine, near Rhiw, Lleyn Peninsula,
Gwennyd, Wales. In the Meldon quarry, Okehampton, Devon,
and the Treburland mine, Altarnun, Cornwall, England.
At Val Malenco, Lombardy, Italy. From Bonneval-sur-Arc,
Haute-Maurienne, Isère, France. Large crystals
from the Wessels mine, near Kuruman, Cape Province,
South Africa. In the Kaso mine, Totigi Prefecture, and
the Noda-Tamagawa mine, Iwate Prefecture, Japan. From
Broken Hill and Tamworth, New South Wales, Australia.
On the Clark Peninsula, Wilkes Land, Antarctica.
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