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About PoldervaartiteHide

colourless, milky white, pink-white
Vitreous, Sub-Vitreous
Specific Gravity:
Crystal System:
For Arie Poldervaart (1918-1964), petrologist, Columbia University, New York.
The Ca-dominant analogue of Olmiite.

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

Visit gemdat.org for gemological information about Poldervaartite.

Classification of PoldervaartiteHide

Approval Year:

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

78 : Unclassified Silicates
1 : Miscellaneous

Pronounciation of PoldervaartiteHide

PlayRecorded byCountry
Jolyon & Katya RalphUnited Kingdom

Physical Properties of PoldervaartiteHide

Vitreous, Sub-Vitreous
Transparent, Translucent
Vitreous on fractures
colourless, milky white, pink-white
Very brittle
None Observed
2.91(2) g/cm3 (Measured)    2.9 g/cm3 (Calculated)

Optical Data of PoldervaartiteHide

Biaxial (+)
RI values:
nα = 1.634 nβ = 1.640 nγ = 1.656
Measured: 63° to 65°, Calculated: 64°
Max Birefringence:
δ = 0.022
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
r < v weak
X= colorless
Y= light gray
Z= bluish gray

Chemical Properties of PoldervaartiteHide

IMA Formula:
Common Impurities:

Crystallography of PoldervaartiteHide

Crystal System:
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Cell Parameters:
a = 9.398(1) Å, b = 9.139(2) Å, c = 10.535(2) Å
a:b:c = 1.028 : 1 : 1.153
Unit Cell V:
904.83 ų (Calculated from Unit Cell)
Prismatic, sheaves

X-Ray Powder DiffractionHide

Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Type Occurrence of PoldervaartiteHide

Place of Conservation of Type Material:
American Museum Natural History, New York T100728

Synonyms of PoldervaartiteHide

Other Language Names for PoldervaartiteHide

Relationship of Poldervaartite to other SpeciesHide

Common AssociatesHide

Associated Minerals Based on Photo Data:
Bultfonteinite10 photos of Poldervaartite associated with Bultfonteinite on mindat.org.
Olmiite6 photos of Poldervaartite associated with Olmiite on mindat.org.
Xonotlite6 photos of Poldervaartite associated with Xonotlite on mindat.org.
Jennite1 photo of Poldervaartite associated with Jennite on mindat.org.
Manganvesuvianite1 photo of Poldervaartite associated with Manganvesuvianite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

9.AF.05SillimaniteAl2(SiO4)OOrth. mmm (2/m 2/m 2/m)
9.AF.10AndalusiteAl2(SiO4)OOrth. mmm (2/m 2/m 2/m) : Pnnm
9.AF.10KanonaiteMn3+Al(SiO4)OOrth. mmm (2/m 2/m 2/m) : Pnnm
9.AF.15KyaniteAl2(SiO4)OTric. 1 : P1
9.AF.20MulliteAl4+2xSi2-2xO10-xOrth. mmm (2/m 2/m 2/m) : Pbam
9.AF.20Krieselite(Al,Ga)2(GeO4)(OH)2Orth. mmm (2/m 2/m 2/m) : Pnma
9.AF.23BoromulliteAl9BSi2O19Orth. mm2 : Cmc21
9.AF.25YoderiteMg(Al,Fe3+)3(SiO4)2O(OH)Mon. 2/m : P21/m
9.AF.30MagnesiostauroliteMg(Mg,Li)3(Al,Mg)18Si8O44(OH)4Mon. 2/m : B2/m
9.AF.30StauroliteFe2+2Al9Si4O23(OH)Mon. 2/m : B2/m
9.AF.30ZincostauroliteZn2Al9Si4O23(OH)Mon. 2/m : B2/m
9.AF.35TopazAl2(SiO4)(F,OH)2Orth. mmm (2/m 2/m 2/m)
9.AF.40NorbergiteMg3(SiO4)(F,OH)2Orth. mmm (2/m 2/m 2/m)
9.AF.45AlleghanyiteMn2+5(SiO4)2(OH)2Mon. 2/m : P21/b
9.AF.45Chondrodite(Mg,Fe2+)5(SiO4)2(F,OH)2Mon. 2/m : P21/b
9.AF.45ReinhardbraunsiteCa5(SiO4)2(OH,F)2Mon. 2/m : P21/b
9.AF.45KumtyubeiteCa5(SiO4)2F2Mon. 2/m : P21/b
9.AF.45HydroxylchondroditeMg5(SiO4)2(OH)2Mon. 2/m : P21/b
9.AF.50Humite(Mg,Fe2+)7(SiO4)3(F,OH)2Orth. mmm (2/m 2/m 2/m) : Pnma
9.AF.50Unnamed (Ca-analogue of Humite)Ca7(SiO4)4F2Orth. mmm (2/m 2/m 2/m)
9.AF.55ClinohumiteMg9(SiO4)4F2Mon. 2/m : P21/b
9.AF.55HydroxylclinohumiteMg9(SiO4)4(OH)2Mon. 2/m
9.AF.60LeucophoeniciteMn2+7(SiO4)3(OH)2Mon. 2/m : P21/b
9.AF.70JerrygibbsiteMn2+9(SiO4)4(OH)2Orth. mmm (2/m 2/m 2/m) : Pbcn
9.AF.75WeliniteMn2+6(W6+,Mg)2(SiO4)2(O,OH)6Trig. 3 : P3
9.AF.85Chloritoid(Fe2+,Mg,Mn2+)Al2(SiO4)O(OH)2Mon. 2/m : B2/b
9.AF.85MagnesiochloritoidMgAl2(SiO4)O(OH)2Mon. 2/m : B2/b
9.AF.90OlmiiteCaMn2+[SiO3(OH)](OH)Orth. mmm (2/m 2/m 2/m) : Pbca

Fluorescence of PoldervaartiteHide

Deep red in SW

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for PoldervaartiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Day, Y., Harlow G.E., and McGhie, A.R. (1993) American Mineralogist, 78, 1082-1087.
New Minerals (1997), New Minerals 1990-1994.
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 PoldervaartiteHide

Localities for PoldervaartiteHide

This 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.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
South Africa (TL)
  • Northern Cape
    • Kalahari manganese field
      • Hotazel
Amer.Min.(1993) 78, 1082-1087; von Bezing, L. & Gutzmer, J. (1994): Das Kalahari Manganerzfeld und seine Mineralien (II). Mineralien-Welt, 5(5), 41-59. Gutzmer, J. & Cairncross, B. (2001): Seltene Mineralien aus dem Kalahari-Manganerzfeld, Südafrika. Lapis, 26(10), 32-42; Gutzmer, J. & Cairncross, B. (2002): Spectacular Minerals from the Kalahari Manganese Field, South Africa. Rocks & Minerals, 77(2), 94-107.
      • Kuruman
        • N'Chwaning Mines
No reference listed
• Cairncross, B., Gutzmer, J. & Pretorius, A. (2002): Spektakulärer Neufund: Poldervaartit aus der N'Chwaning II - Mine, Kalahari, Südafrika. Lapis, 27(5), 30-34; 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.. Pagano et al (2008) Mineralogical Record 39:373-381
Mineral and/or Locality  
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