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Olmiite

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Big Photo

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

Show Olmiite Photos (267)



Formula:
CaMn
2+
 
(HSiO
 
4
)(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+
 
(HSiO
 
4
)(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(HSiO
 
4
)(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
  • Look for Olmiite images on Google
    • External Links:
  • Look for Olmiite on Webmineral
  • Look for Olmiite on Athena Mineralogy
  • Look for Olmiite on Mineralien Atlas
  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Mineral Dealers:
  • Fabre Minerals - search for Olmiite specimens
  • Search for Olmiite from all mineral dealers at minfind.com
  • Search for - Olmiite - on e-Rocks Mineral Sales & Auctions
  • The Arkenstone - Fine Minerals
  • Top quality minerals from Kristalle of California
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  • Buy fine minerals and gemstones from Pala International
  • Fine Minerals from Weinrich Minerals, Inc.
  • Wilensky Fine Minerals
  • Visit the Pueblo Gem and Mineral show, Tucson 2012
    • Specimens:The following Olmiite specimens are currently listed for sale on minfind.com.
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    • Localities for Olmiite

    Hide Locality List
    (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
        • 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.
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    Copyright © Jolyon Ralph and Ida Chau 1993-2011. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Further information contact the Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of hundreds of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
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