Gamagarite
A valid IMA mineral species - grandfathered
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About Gamagarite
Formula:
Ba2Fe3+(VO4)2(OH)
Colour:
Dark brown to black
Lustre:
Adamantine
Hardness:
4½ - 5
Specific Gravity:
4.62
Crystal System:
Monoclinic
Member of:
Name:
After the Gamagara Ridge, South Africa, the type locality.
Type Locality:
Unique Identifiers
Mindat ID:
1645
Long-form identifier:
mindat:1:1:1645:8
IMA Classification of Gamagarite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ba2Fe3+(V5+O4)2(OH)
First published:
1943
Classification of Gamagarite
8.BG.05
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
G : With medium-sized and large cations, (OH, etc.):RO4 = 0.5:1
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
G : With medium-sized and large cations, (OH, etc.):RO4 = 0.5:1
41.10.4.3
41 : ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
10 : (AB)3(XO4)2Zq
41 : ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
10 : (AB)3(XO4)2Zq
21.2.16
21 : Vanadates (and vanadates with arsenate or phosphate)
2 : Vanadates of Mg, Ca, Sr or Ba
21 : Vanadates (and vanadates with arsenate or phosphate)
2 : Vanadates of Mg, Ca, Sr or Ba
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Gam | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Gamagarite
Adamantine
Transparency:
Transparent
Colour:
Dark brown to black
Streak:
Reddish brown
Hardness:
4½ - 5 on Mohs scale
Cleavage:
Distinct/Good
{001} and {100}, distinct; {101} difficult.
{001} and {100}, distinct; {101} difficult.
Density:
4.62 g/cm3 (Measured) 4.72 g/cm3 (Calculated)
Optical Data of Gamagarite
Type:
Biaxial (+)
RI values:
nα = 2.016 nβ = 2.04 nγ = 2.13
2V:
Measured: 46° to 62°, Calculated: 58°
Max. Birefringence:
δ = 0.114
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
relatively weak
Optical Extinction:
Y = b; X ∧ c = 39°–43°.
Pleochroism:
Visible
Comments:
X = red-brown; Y = very deep red-brown; Z = light salmon-buff.
Comments:
Absorption: Y > X > Z.
Chemistry of Gamagarite
Mindat Formula:
Ba2Fe3+(VO4)2(OH)
Element Weights:
Crystallography of Gamagarite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/m
Setting:
P21/m
Cell Parameters:
a = 9.15 Å, b = 6.17 Å, c = 7.88 Å
β = 112.7°
β = 112.7°
Ratio:
a:b:c = 1.483 : 1 : 1.277
Unit Cell V:
410.41 ų (Calculated from Unit Cell)
Z:
2
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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CIF File Best | x | y | z | a | b | c
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Labels
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0014817 | Gamagarite | Basso R, Palenzona A, Zefiro L (1987) Gamagarite: new occurrence and crystal structure refinement Neues Jahrbuch fur Mineralogie, Monatshefte 1987 295-304 | 1987 | a manganese ore deposit at Molinello mine, Val Graveglia, Eastern Liguria, Italy | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.309 Å | (100) |
| 3.051 Å | (80) |
| 2.805 Å | (80) |
| 2.349 Å | (50) |
| 4.969 Å | (10) |
| 4.627 Å | (10) |
| 3.711 Å | (10) |
Comments:
Gloucester Farm, South Africa. Data from Harlow et al. (1984).
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 22 : Hydration and low-? subsurface aqueous alteration (see also #23) | |
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47d : [Arsenates, antimonates, selenates, bismuthinates] |
Type Occurrence of Gamagarite
General Appearance of Type Material:
Aggregates of needles, approximately one centimeter in length, and also as somewhat flattened prisms.
Place of Conservation of Type Material:
The Natural History Museum, London, England, number 1958,553.
National Museum of Natural History, Washington, D.C., USA, number 105142.
National Museum of Natural History, Washington, D.C., USA, number 105142.
Geological Setting of Type Material:
Banded manganese ore.
Associated Minerals at Type Locality:
Other Language Names for Gamagarite
Relationship of Gamagarite to other Species
Member of:
Other Members of Brackebuschite Supergroup:
| Aldomarinoite | Sr2Mn3+(AsO4)2(OH) | Mon. 2/m : P21/m |
| Arsenbrackebuschite | Pb2Fe3+(AsO4)2(OH) | Mon. 2/m : P2/m |
| Arsentsumebite | Pb2Cu(AsO4)(SO4)(OH) | Mon. 2/m : P21/m |
| Bearthite | Ca2Al(PO4)2(OH) | Mon. 2/m : P21/m |
| Brackebuschite | Pb2Mn3+(VO4)2(OH) | Mon. 2/m : P21/m |
| Bushmakinite | Pb2Al(PO4)(VO4)(OH) | Mon. 2/m : P21/m |
| Calderónite | Pb2Fe3+(VO4)2(OH) | Mon. 2/m : P21/m |
| Canosioite | Ba2Fe3+(AsO4)2(OH) | Mon. 2/m : P21/m |
| Feinglosite | Pb2Zn(AsO4)2 · H2O | Mon. 2/m |
| Ferribushmakinite | Pb2Fe3+(PO4)(VO4)(OH) | Mon. 2/m : P21/m |
| Goedkenite | Sr2Al(PO4)2(OH) | Mon. 2/m : P21/m |
| Grandaite | Sr2Al(AsO4)2(OH) | Mon. 2/m : P21/m |
| Lombardoite | Ba2Mn3+(AsO4)2(OH) | Mon. 2/m : P21/m |
| Tokyoite | Ba2Mn3+(VO4)2(OH) | Mon. 2/m : P21/m |
| Tsumebite | Pb2Cu(PO4)(SO4)(OH) | Mon. 2/m : P21/m |
| 'Unnamed (possible ordered As-analogue of Tokyoite)' | Ba2Mn[(As,V)O4]2(OH) | Mon. 2/m : P21/m |
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 8.BG. | Aldomarinoite | Sr2Mn3+(AsO4)2(OH) |
| 8.BG. | Dongchuanite | Pb4ZnZn2(PO4)4(OH)2 |
| 8.BG. | Cuprodongchuanite | Pb4CuZn2(PO4)4(OH)2 |
| 8.BG. | Canosioite | Ba2Fe3+(AsO4)2(OH) |
| 8.BG.05 | Feinglosite | Pb2Zn(AsO4)2 · H2O |
| 8.BG.05 | Tokyoite | Ba2Mn3+(VO4)2(OH) |
| 8.BG.05 | Lombardoite | Ba2Mn3+(AsO4)2(OH) |
| 8.BG.05 | Bearthite | Ca2Al(PO4)2(OH) |
| 8.BG.05 | 'Unnamed (possible ordered As-analogue of Tokyoite)' | Ba2Mn[(As,V)O4]2(OH) |
| 8.BG.05 | Arsentsumebite | Pb2Cu(AsO4)(SO4)(OH) |
| 8.BG.05 | 'UM1994-19-PO:CuHMoPb' | Pb2Cu(PO4)(MoO4,AsO4,CrO4,GaO4)(OH) |
| 8.BG.05 | Ferribushmakinite | Pb2Fe3+(PO4)(VO4)(OH) |
| 8.BG.05 | Arsenbrackebuschite | Pb2Fe3+(AsO4)2(OH) |
| 8.BG.05 | Goedkenite | Sr2Al(PO4)2(OH) |
| 8.BG.05 | Tsumebite | Pb2Cu(PO4)(SO4)(OH) |
| 8.BG.05 | Brackebuschite | Pb2Mn3+(VO4)2(OH) |
| 8.BG.05 | Bushmakinite | Pb2Al(PO4)(VO4)(OH) |
| 8.BG.05 | Calderónite | Pb2Fe3+(VO4)2(OH) |
| 8.BG.10 | Mélonjosephite | CaFe2+Fe3+(PO4)2(OH) |
| 8.BG.15 | Tancoite | LiNa2Al(PO4)(PO3OH)(OH) |
| 8.BG.20 | Dmisokolovite | K3Cu5AlO2(AsO4)4 |
| 8.BG.25 | Shchurovskyite | K2CaCu6O2(AsO4)4 |
| 8.BG.30 | Wrightite | K2Al2O(AsO4)2 |
| 8.BG.35 | Polyarsite | Na7CaMgCu2(AsO4)4F2Cl |
Other Information
Magnetism:
Ferromagnetic
Notes:
Moderately magnetic.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Gamagarite
mindat.org URL:
https://www.mindat.org/min-1645.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Gamagarite
Reference List:
de Villiers, J. E. (1943) Gamagarite, a new vanadium mineral from the Postmasburg manganese deposits. American Mineralogist, 28 (5) 329-335
Localities for Gamagarite
Showing 12 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Argentina | |
| Rainoldi et al. (2024) |
Austria | |
| Kolitsch et al. (2018) |
Italy | |
| 415. +1 other reference |
| 415 (365) +1 other reference |
| Castellaro et al. (2023) |
| Balestra (2006) |
| analysed by Dr. Anthony Kampf |
| Bracco R. (2014) +2 other references |
Japan | |
| Matsubara (2004) |
South Africa (TL) | |
| de Villiers (1943) +1 other reference |
| Gutzmer (1996) +1 other reference |
| Costin et al. (2014) |
Quick NavTopAbout GamagariteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesRelationshipsCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Molinello Mine, Ne, Genoa, Liguria, Italy