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Olmiite

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N'Chwaning II Mine, N'Chwaning Mines, Kalahari manganese fields, Northern Cape Province, South Africa
© Rob Lavinsky

Show Olmiite Photos (2)
Formula:
CaMn
2+
 
[SiO
 
3
(OH)](OH)
System:OrthorhombicColour:Pale to intense reddish ...
Hardness:5 - 5½


Mn2+-dominant analogue of Poldervaartite.

A product of hydrothermal alteration.

Classification of Olmiite

IMA status:Approved 2006
Strunz 8th edition ID:8/B.22-22
Nickel-Strunz 10th (pending) edition ID:9.AF.90

9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
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Type Occurrence of Olmiite

Type Locality:N'Chwaning II Mine, N'Chwaning Mines, Kalahari manganese fields, Northern Cape Province, South Africa
General Appearance of Type Material:Wheat sheaf aggregates.
Year of Discovery:2006
Associated Minerals at type locality:
SturmanitePoldervaartiteHematiteCelestineBultfonteinite

Physical Properties of Olmiite

Lustre:Vitreous
Diaphaneity (Transparency):Transparent
Colour:Pale to intense reddish pink.
Streak:White
Hardness (Mohs):5 - 5½
Tenacity:Brittle
Cleavage:None Observed
Fracture:Irregular/Uneven
Density (measured):3.05 g/cm3
Density (calculated):3.102 g/cm3
Comment:Calculated value based on unit cell volume; a value of 3.109 from powder data.

Crystallography of Olmiite

Crystal System:Orthorhombic
Class (H-M):mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:Pbca (P21/b 21/c 21/a)
Cell Parameters:a = 9.249Å, b = 9.076Å, c = 10.342Å
Ratio:a:b:c = 1.019 : 1 : 1.139
Unit Cell Volume:V 868 ų
Z:8
Morphology:Crystals minute. Aggregates resemble wheat sheaves.
X-Ray Powder Diffraction:
d-spacingIntensity
4.14 (60)
4.10 (30)
3.19 (100)
2.807 (35)
2.762 (30)
2.545 (35)
2.521 (30)

Optical Data of Olmiite

Type:Biaxial (+)
RI values: nα = 1.663(1) nβ = 1.672(1) nγ = 1.694(1)
2V:Measured: 71° , Calculated: 66°
Maximum Birefringence:δ = 0.031

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:High
Dispersion:r > v distinct
Pleochroism:Non-pleochroic

Chemical Properties of Olmiite

Formula:
CaMn
2+
 
[SiO
 
3
(OH)](OH)
Essential elements:
All elements listed in formula:Ca, H, Mn, O, Si

Relationship of Olmiite to other Species

Related Minerals - Nickel-Strunz Grouping):
9.AF.05Sillimanite
Al
 
2
[O|SiO
 
4
]
9.AF.10Andalusite
Al
 
2
[O|SiO
 
4
]
9.AF.10Kanonaite
Mn
3+
 
Al[O|SiO
 
4
]
9.AF.15Kyanite
Al
 
2
[O|SiO
 
4
]
9.AF.20Mullite
Al
 
8
[(O,OH,F)|(Si,Al)O
 
4
]
 
4
9.AF.20Krieselite
(Al,Ga)
 
2
[(OH)
 
2
|GeO
 
4
]
9.AF.25Yoderite
Mg(Al,Fe
3+
 
)
 
3
[O|OH|(SiO
 
4
)
 
2
]
9.AF.30Magnesiostaurolite
(Mg,Li,Fe
2+
 
)
 
1.5-2
Al
 
9
[O
 
6
|(OH)
 
2
|(SiO
 
4
)
 
4
]
9.AF.30Staurolite
(Fe
2+
 
,Mg,Zn)
 
1.5-2
Al
 
9
[O
 
6
|(OH,O)
 
2
|(SiO
 
4
)
 
4
]
9.AF.30Zincostaurolite
(Zn,Li,Fe
2+
 
,Mg)
 
<2
Al
 
9
[O
 
6
|(OH)
 
2
|(SiO
 
4
)
 
4
]
9.AF.35Topaz
Al
 
2
[(F,OH)
 
2
|SiO
 
4
]
9.AF.40Norbergite
Mg
 
3
[(F,OH)
 
2
|SiO
 
4
]
9.AF.45Alleghanyite
Mn
2+
5
[(OH)
 
2
|(SiO
 
4
)
 
2
]
9.AF.45Chondrodite
(Mg,Fe
2+
 
)
 
5
[(F,OH)
 
2
|(SiO
 
4
)
 
2
]
9.AF.45Reinhardbraunsite
Ca
 
5
[(OH,F)
 
2
|(SiO
 
4
)
 
2
]
9.AF.50Humite
(Mg,Fe
2+
 
)
 
7
[(F,OH)
 
2
|(SiO
 
4
)
 
3
]
9.AF.50Manganhumite
(Mn
2+
 
,Mg)
 
7
[(OH)
 
2
|(SiO
 
4
)
 
3
]
9.AF.55Clinohumite
(Mg,Fe
2+
 
)
 
9
[(F,OH)
 
2
|(SiO
 
4
)
 
4
]
9.AF.55Sonolite
Mn
2+
9
[(OH,F)
 
2
|(SiO
 
4
)
 
4
]
9.AF.55Hydroxylclinohumite
Mg
 
9
[(OH,F)
 
2
|(SiO
 
4
)
 
4
]
9.AF.60Leucophoenicite
Mn
2+
7
[(OH)
 
2
|(SiO
 
4
)
 
3
]
9.AF.65Ribbeite
(Mn
2+
 
,Mg)
 
5
[(OH)
 
2
|(SiO
 
4
)
 
2
]
9.AF.70Jerrygibbsite
Mn
2+
9
[(OH)
 
2
|(SiO
 
4
)
 
4
]
9.AF.75Franciscanite
Mn
3+
6
V
5+
0.5
[(O,OH)
 
3
|SiO
 
4
]
9.AF.75Örebroite
Mn
2+
3
(Fe
3+
 
,Sb
5+
 
)[(O,OH)
 
3
|SiO
 
4
]
9.AF.75Welinite
Mn
3+
6
(W
6+
 
,Mg)
 
0.7
[(O,OH)
 
3
|SiO
 
4
]
9.AF.80Ellenbergerite
Mg
 
6
Al
 
6
Ti[(OH)
 
6
|(HSiO
 
4
)
 
4
|(SiO
 
4
)
 
4
]
9.AF.85Chloritoid
(Fe
2+
 
,Mg,Mn
2+
 
)Al
 
2
[O|(OH)
 
2
|SiO
 
4
]
9.AF.85Magnesiochloritoid
MgAl
 
2
[O|(OH)
 
2
|SiO
 
4
]
9.AF.85Ottrélite
(Mn
2+
 
,Fe
2+
 
,Mg)Al
 
2
[O|(OH)
 
2
|SiO
 
4
]
9.AF.90Poldervaartite
CaCa[SiO
 
3
OH](OH)

Other Names for Olmiite

Synonyms:
IMA2006-026Olmiit

Other Information

Fluorescence in UV light:Deep red (SW UV)
Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Olmiite

Reference List:Bonazzi, P., Bindi, L., Medenbach, O., Pagano, R., Lampronti, Menchetti, S. (2007): Olmiite, CaMn[SiO3(OH)](OH), the Mn-dominant analogue of poldervaartite, a new mineral species from Kalahari manganese fields (Republic of South Africa), Mineralogical Magazine, 71, 193-291.

Internet Links for Olmiite

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    Localities for Olmiite

    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    South Africa
     
    • Northern Cape Province
      • Kalahari manganese fields
        • N'Chwaning Mines
    		Bonazzi, P., Bindi, L., Medenbach, O., Pagano, R., Lampronti, Menchetti, S. (2007): Olmiite, CaMn[SiO3(OH)](OH), the Mn-dominant analogue of poldervaartite, a new mineral species from Kalahari manganese fields (Republic of South Africa), Mineralogical Magazine, 71, 193-291.
    Mineral and/or Locality
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