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| Bertossaite
was named to honor Antonio Bertossa, Director of the
Geological Survey of Rwanda, the country in which it was first found.
| Discovered
in 1965; IMA
status:
Valid (IMA Approved 1965) |
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Chemistry
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Chemical
Formula: |
(Li,Na)2(Ca,Fe2+,Mn2+)Al4(PO4)4(OH,F)4
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Lithium
Sodium Calcium Iron Manganese Aluminum Phosphate Hydroxide
Fluoride |
Molecular
Weight: |
609.80 gm
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Composition: |
Lithiium |
2.28 % |
Li |
4.90 % |
Li2O |
|
Calcium |
6.57 % |
Ca |
9.20 % |
CaO |
|
Aluminum |
17.70 % |
Al |
33.44 % |
Al2O3 |
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Phosphorus |
20.32 % |
P |
46.55 % |
P2O5 |
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Hydrogen |
0.66 % |
H |
5.91 % |
H2O |
|
Oxygen |
52.47 % |
O |
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|
|
100.00 % |
|
100.00 % |
= TOTAL OXIDE |
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Classification
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Mineral
Classification: |
Phosphates
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Strunz 8th
Ed. ID:
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8/B.28-10
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Nickel-Strunz 10th
Ed. ID:
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8.BH.25
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8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
H : With medium-sized and large cations, (OH,etc.):RO4 = 1:1
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Related
to: |
Bertossaite-Palermoite Series. The calcium analogue of Palermoite.
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Varieties: |
None
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Synonyms: |
IMA1965-038
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Crystal
Data
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Crystallography:
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Orthorhombic
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Crystal
Habit:
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Massive
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Twinning:
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None
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Physical
Properties
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Cleavage: |
Good
on {100}
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Fracture: |
Irregular/Uneven
to sub-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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3.10 (g/cm3)
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Luminescence:
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None
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Radioactivity:
|
Not
Radioactive
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Optical
Properties
|
|
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Color: |
Pale
pink; colorless in transmitted light
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Transparency: |
Semi-transparent |
Luster: |
Vitreous |
Refractive
Index: |
1.624
- 1.642 Biaxial ( - )
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Birefringence: |
0.018
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Dispersion: |
Moderately strong, r < v |
Pleochroism: |
None |
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Occurances
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Geological
Setting: |
Thought
to be formed during a late calcium-rich phase of mineralization
in a lithium-bearing granite pegmatite. |
Common
Associations: |
Amblygonite,
Lazulite-Scorzalite, Augelite, Brazilianite, Apatite,
Crandallite, Trolleite, Samuelsonite, Quartz |
Common
Impurities: |
Fe,
Mn |
Type
Locality: |
Buranga pegmatite, Gatumba District, Western Province, Rwanda
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Year
Discovered: |
1965
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View
mineral photos: |
Bertossaite
Mineral Photos and Locations |
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More
Information
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|
Mindat.org
Webmineral.com
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Bertossaite
is a rare
phosphate mineral from the Buranga lithium pegmatite
in Rwanda. It was originally described by Oleg
von Knorring in 1965 from samples found in the
Buranga pegmatite, Gatumba District, Western Province,
Rwanda. He investigated the chemical properties in 1965
but the physical properties of Bertossaite were later determined
by von Knorring and Mary E. Mrose in 1966. Bertossaite
was named to honor Antonio Bertossa, Director of the
Geological Survey of Rwanda.
For
more than 35 years after its discovery Bertossaite was
thought to be a one locatlity mineral until in 2003
Pierre Lefèvre investigated new samples of phosphates
from the Rubindi-Kabilizi pegmatite, Rwanda, and discovered
a new occurrence of Bertossaite in veins cross-cutting
Montebrasite, Scorzalite, and Brazilianite. This investigation
was part of Lefèvre's Master’s thesis at
the University of Liège, Liège, Belgium.
Bertossaite is often found associated with Apatite,
Brazilianite, Burangaite,
Quartz,
Scorzalite
and Trolleite.
The
picture above shows a gem with faintly-pink to white
Bertossaite with blue Burangaite.
Bertossaite is typically semi-transparent with vitreous
luster and moderately strong dispersion and a Moh's
hardness of 6. The combination of faintly pink to white
Bertossaite and royal blue Burangaite makes for very
attractive specimens and gems.
Bertossaite
distribution: at the type locality in the
Buranga pegmatite, near Gatumba, Rwanda. Also at the
Rubindi-Kabilizi pegmatite, located 3 km WNW of Muhororo village, south of the Rubindi river, 50 km west of Kigali, Rwanda.
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