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Olmiite

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Big Photo

Wessels Mine (Wessel's Mine), Hotazel, Kalahari manganese fields, Northern Cape Province, South Africa
© Rob Lavinsky

Show Olmiite Photos (323)



Formula:
CaMn
2+
 
[SiO
 
3
(OH)](OH)
System:OrthorhombicColour:Pale to intense reddish ...
Hardness:5 - 5½
Name:Named for Filippo Olmi (CNR, Centre di Studio per la Minerogenesi ela Geochimica Applicata, Florence, Italy)


Mn2+-dominant analogue of Poldervaartite.

A product of hydrothermal alteration.

Most (all?) "poldervaartites" seem to be olmiites, see http://www.mindat.org/mesg-7-104499.html.

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
mindat.org URL:http://www.mindat.org/min-30762.html
Please feel free to link to this page.

Type Occurrence of Olmiite

Type Locality:N'Chwaning II Mine, N'Chwaning Mines, Kuruman, 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)
2.361 (40)

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:Ca, H, Mn, O, Si
All elements listed in formula:Ca, H, Mn, O, Si

Relationship of Olmiite to other Species

Series:Forms a series with Poldervaartite (see here)
Related Minerals - Nickel-Strunz Grouping):

- +
9.AF.05Sillimanite
Al
 
2
(SiO
 
4
)O
9.AF.10Andalusite
Al
 
2
(SiO
 
4
)O
9.AF.10Kanonaite
Mn
3+
 
Al(SiO
 
4
)O
9.AF.15Kyanite
Al
 
2
(SiO
 
4
)O
9.AF.20Mullite
Al
 
4+2x
Si
 
2-2x
O
 
10-x
9.AF.20Krieselite
(Al,Ga)
 
2
(GeO
 
4
)(OH)
 
2
9.AF.23Boromullite
Al
 
9
BSi
 
2
O
 
19
9.AF.25Yoderite
Mg(Al,Fe
3+
 
)
 
3
(SiO
 
4
)
 
2
O(OH)
9.AF.30Magnesiostaurolite
(Mg,Li,Fe
2+
 
)
 
1.5-2
Al
 
9
(SiO
 
4
)
 
4
O
 
6
(OH)
 
2
9.AF.30Staurolite
(Fe
2+
 
,Mg,Zn)
 
1.5-2
Al
 
9
(SiO
 
4
)
 
4
O
 
6
(OH,O)
 
2
9.AF.30Zincostaurolite
(Zn,Li,Fe
2+
 
,Mg)
 
1.5-2
Al
 
9
(SiO
 
4
)
 
4
O
 
6
(OH)
 
2
9.AF.35Topaz
Al
 
2
(SiO
 
4
)(F,OH)
 
2
9.AF.40Norbergite
Mg
 
3
(SiO
 
4
)(F,OH)
 
2
9.AF.45Alleghanyite
Mn
2+
5
(SiO
 
4
)
 
2
(OH)
 
2
9.AF.45Chondrodite
(Mg,Fe
2+
 
)
 
5
(SiO
 
4
)
 
2
(F,OH)
 
2
9.AF.45Reinhardbraunsite
Ca
 
5
(SiO
 
4
)
 
2
(OH,F)
 
2
9.AF.45Kumtyubeite
Ca
 
5
(SiO
 
4
)
 
2
F
 
2
9.AF.45Hydroxylchondrodite
Mg
 
5
(SiO
 
4
)
 
2
(OH)
 
2
9.AF.50Humite
(Mg,Fe
2+
 
)
 
7
(SiO
 
4
)
 
3
(F,OH)
 
2
9.AF.50Manganhumite
(Mn
2+
 
,Mg)
 
7
(SiO
 
4
)
 
3
(OH)
 
2
9.AF.50Unnamed (Ca-analogue of Humite)
Ca
 
7
(SiO
 
4
)
 
4
F
 
2
9.AF.55Clinohumite
(Mg,Fe
2+
 
)
 
9
(SiO
 
4
)
 
4
(F,OH)
 
2
9.AF.55Sonolite
Mn
2+
9
(SiO
 
4
)
 
4
(OH,F)
 
2
9.AF.55Hydroxylclinohumite
Mg
 
9
(SiO
 
4
)
 
4
(OH,F)
 
2
9.AF.60Leucophoenicite
Mn
2+
7
(SiO
 
4
)
 
3
(OH)
 
2
9.AF.65Ribbeite
(Mn
2+
 
,Mg)
 
5
(SiO
 
4
)
 
2
(OH)
 
2
9.AF.70Jerrygibbsite
Mn
2+
9
(SiO
 
4
)
 
4
(OH)
 
2
9.AF.75Franciscanite
Mn
2+
6
(V
5+
 
,☐)
 
2
(SiO
 
4
)
 
2
(O,OH)
 
6
9.AF.75Örebroite
Mn
2+
3
(Fe
3+
 
,Sb
5+
 
)(SiO
 
4
)(O,OH)
 
3
9.AF.75Welinite
Mn
2+
6
(W
6+
 
,Mg)
 
2
(SiO
 
4
)
 
2
(O,OH)
 
6
9.AF.80Ellenbergerite
Mg
 
6
(Mg,Ti,Zr,◻)
 
2
(Al,Mg)
 
6
Si
 
8
O
 
28
(OH)
 
10
9.AF.85Chloritoid
(Fe
2+
 
,Mg,Mn
2+
 
)Al
 
2
(SiO
 
4
)O(OH)
 
2
9.AF.85Magnesiochloritoid
MgAl
 
2
(SiO
 
4
)O(OH)
 
2
9.AF.85Ottrélite
(Mn
2+
 
,Fe
2+
 
,Mg)Al
 
2
(SiO
 
4
)O(OH)
 
2
9.AF.90Poldervaartite
CaCa[SiO
 
3
(OH)](OH)

Other Names for Olmiite

Synonyms:
IMA2006-026Olmiit
Other Languages:

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

Search Engines:
  • Look for Olmiite on Google
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    • External Links:
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  • Look for Olmiite on Mineralien Atlas
  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
    • Mineral Dealers:
  • Find Olmiite on www.crystalclassics.co.uk
  • Wilensky Fine Minerals
  • Fabre Minerals - search for Olmiite specimens
  • Mineral Classics - Worldwide Collector Quality Minerals and Gems
  • Search for Olmiite on Well-Arranged Molecules
  • SpiriferMinerals.com - high quality low prices
  • Olmiite specimens for sale - minfind.com
  • Search for - Olmiite - on e-Rocks Mineral Sales & Auctions
  • Search for minerals at Heliodor
  • Top quality minerals from Kristalle of California
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    • Specimens:The following Olmiite specimens are currently listed for sale on minfind.com.
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    • Localities for Olmiite

    The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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    (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
        • Hotazel
    		http://www.mindat.org/mesg-7-104499.html.
        • Kuruman
          • 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.
    P.Rondelez
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