Walstromite
A valid IMA mineral species
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About Walstromite
Little Mildred Mine Lower Adit
Little Mildred mine, Sylvanite Mining District, Hidalgo County, New Mexico, USA
Little Mildred mine, Sylvanite Mining District, Hidalgo County, New Mexico, USA
Formula:
BaCa2(Si3O9)
Colour:
Colourless to white
Lustre:
Sub-Vitreous, Pearly
Hardness:
3½
Specific Gravity:
3.67
Crystal System:
Triclinic
Member of:
Name:
Named after Robert "Bob" E. Walstrom (born in Lebanon, Missouri on July 15th, 1937, and passed away on Feb 4th, 2022 in Santa Clara, NM., USA), geologist and mineral collector, formerly of Fresno, CA, later of Silver City, NM, USA. He has 12 minerals new to science to his credit, already published (2008), with more in the works.
Type Locality:
Isostructural with:
The Ba analogue of margarosanite. Chemically similar to macdonaldite which, however, is basic and contains water.
Unique Identifiers
Mindat ID:
4239
Long-form identifier:
mindat:1:1:4239:6
IMA Classification of Walstromite
Approved
IMA Formula:
BaCa2Si3O9
Approval year:
1964
First published:
1965
Classification of Walstromite
9.CA.25
9 : SILICATES (Germanates)
C : Cyclosilicates
A : [Si3O9]6- 3-membered single rings (dreier-Einfachringe), without insular complex anions
9 : SILICATES (Germanates)
C : Cyclosilicates
A : [Si3O9]6- 3-membered single rings (dreier-Einfachringe), without insular complex anions
59.1.2.1
59 : CYCLOSILICATES Three-Membered Rings
1 : Three-Membered Rings, anhydrous, no other anions
59 : CYCLOSILICATES Three-Membered Rings
1 : Three-Membered Rings, anhydrous, no other anions
14.7.3
14 : Silicates not Containing Aluminum
7 : Silicates of Ba, Sr and Zn
14 : Silicates not Containing Aluminum
7 : Silicates of Ba, Sr and Zn
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 |
|---|---|---|
| Ws | 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 Walstromite
Sub-Vitreous, Pearly
Transparency:
Transparent, Translucent
Comment:
Pearly on cleavages
Colour:
Colourless to white
Streak:
White
Hardness:
3½ on Mohs scale
Cleavage:
Perfect
{011}, {010}, and {100}.
{011}, {010}, and {100}.
Density:
3.67(6) g/cm3 (Measured) 3.738 g/cm3 (Calculated)
Optical Data of Walstromite
Type:
Biaxial (-)
RI values:
nα = 1.668(2) nβ = 1.684(2) nγ = 1.685(2)
2V:
Measured: 30° , Calculated: 28°
Max. Birefringence:
δ = 0.017
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:
weak
Chemistry of Walstromite
Mindat Formula:
BaCa2(Si3O9)
Element Weights:
Elements listed:
Common Impurities:
Ti,Al,Fe,Mn,Mg,Sr,K
Crystallography of Walstromite
Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 6.7335 Å, b = 9.6142(3) Å, c = 6.6859(2) Å
α = 69.638(2)°, β = 102.281(2)°, γ = 96.885(2)°
α = 69.638(2)°, β = 102.281(2)°, γ = 96.885(2)°
Ratio:
a:b:c = 0.7 : 1 : 0.695
Unit Cell V:
396.00 ų (Calculated from Unit Cell)
Z:
2
Crystal Structure
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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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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) |
|---|---|---|---|---|---|---|---|
| 0018336 | Walstromite | Barkley M C, Downs R T, Yang H (2011) Structure of walstromite, BaCa2Si3O9, and its relationship to CaSiO3-walstromite and wollastonite-II American Mineralogist 96 797-801 | 2011 | Esquire No. 8 claim, Big Creek, Fresno County, California, U.S.A. | 0 | 293 | |
| 0007324 | Walstromite | Dorsam G, Liebscher A, Wunder B, Franz G, Gottschalk M (2009) Crystal structure refinement of synthetic Ca0.43Sr0.57[SiO3]-walstromite and walstromite-fluid Ca-Sr distribution at upper-mantle conditions European Journal of Mineralogy 21 705-714 | 2009 | synthetic | 0 | 293 | |
| 0014201 | Walstromite | Basciano L C (1999) Mineralogy and crystal structures of barium silicate minerals from Fresno County, California Master's Thesis, University of British Columbia 1999 1-164 | 1999 | Esquire #7, Big Creek, Fresno County, California, USA | 0 | 293 | |
| 0011105 | Walstromite | Joswig W, Paulus E F, Winkler B, Milman V (2003) The crystal structure of CaSiO3-walstromite, a special isomorph of wollastonite-II Zeitschrift fur Kristallographie 218 811-818 | 2003 | 0 | 293 | ||
| 0000165 | Walstromite | Dent Glasser L S, Glasser F P (1968) The crystal structure of walstromite American Mineralogist 53 9-13 |  | 1968 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.99 Å | (100) |
| 6.58 Å | (20) |
| 2.70 Å | (20) |
| 4.40 Å | (15) |
| 3.35 Å | (15) |
| 3.20 Å | (15) |
| 3.06 Å | (15) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-𝑇 alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 51 : Pyrometamorphic minerals (see also #54 and #56) | <0.36 |
Type Occurrence of Walstromite
General Appearance of Type Material:
Individual disseminated grains, or concentrated in layers. Grains reach 12 x 6 x 6 mm.
Place of Conservation of Type Material:
California Division of Mines & Geology, San Francisco, California, USA.
Geological Setting of Type Material:
Sanbornite-quartz rock, especially where the quartz content is high.
Associated Minerals at Type Locality:
Synonyms of Walstromite
Other Language Names for Walstromite
Relationship of Walstromite to other Species
Member of:
Other Members of Margarosanite Group:
| Anatolygurbanovite | SrCa2Si3O9 | Tric. 1 : P1 |
| Breyite | Ca3Si3O9 | Tric. 1 : P1 |
| Margarosanite | Ca2PbSi3O9 | Tric. 1 : P1 |
Common Associates
Associations Based on Photo Data:
| 11 photos of Walstromite associated with Sanbornite | BaSi2O5 |
| 6 photos of Walstromite associated with Quartz | SiO2 |
| 6 photos of Walstromite associated with Margarosanite | Ca2PbSi3O9 |
| 6 photos of Walstromite associated with Celsian | Ba(Al2Si2O8) |
| 5 photos of Walstromite associated with Bazirite | BaZr(Si3O9) |
| 4 photos of Walstromite associated with Aragonite | CaCO3 |
| 3 photos of Walstromite associated with Fresnoite | Ba2Ti(Si2O7)O |
| 3 photos of Walstromite associated with Titantaramellite | Ba4(Ti,Fe3+,Fe2+,Mg)4(B2Si8O27)O2Clx |
| 2 photos of Walstromite associated with Calcite | CaCO3 |
| 1 photo of Walstromite associated with Pyrrhotite | Fe1-xS |
Related Minerals - Strunz-mindat Grouping
| 9.CA. | 'UM1975-18-SiO:Mn' | α-MnSiO3 |
| 9.CA. | Raudseppite | Ba2Ca7(Si3O9)2(CO3)2Cl2 |
| 9.CA. | Kopylovite | K2Ti(Si3O9) |
| 9.CA.05 | Bazirite | BaZr(Si3O9) |
| 9.CA.05 | Benitoite | BaTi(Si3O9) |
| 9.CA.05 | Pabstite | Ba(Sn,Ti)(Si3O9) |
| 9.CA.10 | Wadeite | K2Zr(Si3O9) |
| 9.CA.15 | Calciocatapleiite | CaZr(Si3O9) · 2H2O |
| 9.CA.15 | Catapleiite | Na2Zr(Si3O9) · 2H2O |
| 9.CA.20 | Pseudowollastonite | CaSiO3 |
| 9.CA.25 | Margarosanite | Ca2PbSi3O9 |
| 9.CA.25 | Anatolygurbanovite | SrCa2Si3O9 |
| 9.CA.25 | Breyite | Ca3Si3O9 |
| 9.CA.30 | Bobtraillite | (Na,◻)12(◻,Na)12Sr12Zr14(Si3O9)10[Si2BO7(OH)2]6 · 12H2O |
| 9.CA.35 | Rogermitchellite | Na6Sr12Ba2Zr13Si39B4O123(OH)6 · 20H2O |
Fluorescence of Walstromite
Dull pink under SW UV; bright pink under LW UV.
Other Information
Thermal Behaviour:
Fuses to a clear glass at about 4.
On heating in an electric furnace it shows no change in appearance until 1200 °C, when it partially melts to a colorless glass.
On heating in an electric furnace it shows no change in appearance until 1200 °C, when it partially melts to a colorless glass.
Notes:
Readily decomposed by cold dilute acids leaving a white silica residue, but not affected by bases.
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 Walstromite
mindat.org URL:
https://www.mindat.org/min-4239.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Walstromite
Reference List:
Glasser, F. P., Glasser, L. S. Dent (1961) Crystallographic study of Ca2BaSi3O9. Zeitschrift für Kristallographie - Crystalline Materials, 116 (3) 263-265 doi:10.1524/zkri.1961.116.3-6.263
Glasser, F. P., Dent Glasser, L. S. (1964) Additional notes on margarosanite. American Mineralogist, 49 (5-6) 781-782
Alfors, John T., Stinson, Melvin C., Matthews, Robert A., Pabst, Adolf (1965) Seven new barium minerals from eastern Fresno County, California. American Mineralogist, 50 (3-4) 314-340
Dent Glasser, L. S., Glasser, F. P. (1968) The crystal structure of walstromite. American Mineralogist, 53 (1-2) 9-13
Alfors, John T., Pabst, Adolf (1984) Titanian taramellites in western North America. American Mineralogist, 69 (3-4) 358-373
Barkley, M. C., Downs, R. T., Yang, H. (2011) Structure of walstromite, BaCa2Si3O9, and its relationship to CaSiO3-walstromite and wollastonite-II. American Mineralogist, 96 (5) 797-801 doi:10.2138/am.2011.3699
Gaft, Michael, Yeates, H., Nagli, Lev (2013) Laser-induced time-resolved luminescence of natural margarosanite Pb(Ca,Mn)2Si3O9, swedenborgite NaBe4SbO7 and walstromite BaCa2Si3O9. European Journal of Mineralogy, 25 (1) 71-77 doi:10.1127/0935-1221/2013/0025-2260
Callegari, Athos Maria; Boiocchi, Massimo (2016) Crystal structure refinement of margarosanite PbCa2Si3O9 and relationship with walstromite BaCa2Si3O9. Neues Jahrbuch für Mineralogie - Abhandlungen, 193 (2). 205-213 doi:10.1127/njma/2016/0302
Localities for Walstromite
Showing 24 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.
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Esquire No. 8 claim, Big Creek, Big Creek-Rush Creek Mining District, Fresno County, California, USA