Okayamalite
A valid IMA mineral species
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About Okayamalite
Flag of Okayama Prefecture, Japan
Formula:
Ca2B[BSiO7]
Colour:
cream white
Lustre:
Earthy
Hardness:
5½
Specific Gravity:
3.30 (Calculated)
Crystal System:
Tetragonal
Member of:
Name:
Named after Okayama Prefecture, Japan, which includes the type locality.
This page provides mineralogical data about Okayamalite.
Unique Identifiers
Mindat ID:
7202
Long-form identifier:
mindat:1:1:7202:7
IMA Classification of Okayamalite
Approved
IMA Formula:
Ca2B2SiO7
Approval year:
1997
First published:
1998
Classification of Okayamalite
9.BB.10
9 : SILICATES (Germanates)
B : Sorosilicates
B : Si2O7 groups, without non-tetrahedral anions; cations in tetrahedral [4] and greater coordination
9 : SILICATES (Germanates)
B : Sorosilicates
B : Si2O7 groups, without non-tetrahedral anions; cations in tetrahedral [4] and greater coordination
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 |
|---|---|---|
| Oky | 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 Okayamalite
Earthy
Transparency:
Translucent
Colour:
Cream white
Streak:
White
Hardness:
5½ on Mohs scale
Cleavage:
None Observed
Density:
3.30 g/cm3 (Calculated)
Optical Data of Okayamalite
Type:
Uniaxial (-)
RI values:
nω = 1.700 nε = 1.696
Max. Birefringence:
δ = 0.004
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:
Moderate
Chemistry of Okayamalite
Mindat Formula:
Ca2B[BSiO7]
Element Weights:
Elements listed:
Crystallography of Okayamalite
Crystal System:
Tetragonal
Class (H-M):
42m - Scalenohedral
Space Group:
P421m
Cell Parameters:
a = 7.1248(2) Å, c = 4.8177(2) Å
Ratio:
a:c = 1 : 0.676
Unit Cell V:
244.56 ų (Calculated from Unit Cell)
Z:
2
Crystal Structure
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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) |
|---|---|---|---|---|---|---|---|
| 0002589 | Okayamalite | Giuli G, Bindi L, Bonazzi P (2000) Rietveld refinement of okayamalite, Ca2SiB2O7: Structural evidence for the B/Si ordered distribution American Mineralogist 85 1512-1515 |  | 2000 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.654 Å | (100) |
| 2.862 Å | (55) |
| 3.479 Å | (40) |
| 1.920 Å | (35) |
| 1.644 Å | (29) |
| 2.129 Å | (20) |
| 1.644 Å | (20) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 23 : Subaerial aqueous alteration by non-redox-sensitive fluids (see also #47) |
Type Occurrence of Okayamalite
General Appearance of Type Material:
grains to 10 μm in equigranular aggregates
Place of Conservation of Type Material:
National Science Museum, Tokyo, under the registered number NSM M-27525.
Associated Minerals at Type Locality:
Synonyms of Okayamalite
Other Language Names for Okayamalite
Relationship of Okayamalite to other Species
Member of:
Other Members of Melilite Group:
| Åkermanite | Ca2Mg[Si2O7] | Tet. 42m : P421m |
| Alumoåkermanite | (CaNa)Al[Si2O7] | Tet. 42m : P421m |
| Bennesherite | Ba2Fe2+[Si2O7] | Tet. 42m : P421m |
| 'Ferri-gehlenite' | Ca2Fe3+[AlSiO7] | |
| Ferroåkermanite | Ca2Fe[Si2O7] | Tet. 42m : P421m |
| Gehlenite | Ca2Al[AlSiO7] | Tet. 42m : P421m |
| Gugiaite | Ca2Be[Si2O7] | Tet. 42m : P42m |
| Hardystonite | Ca2Zn[Si2O7] | Tet. 42m : P421m |
| Hydroxylgugiaite | (Ca,◻)2(Si,Be)[(Be,Si)2O5.5(OH)1.5] | Tet. 42m : P421m |
Related Minerals - Strunz-mindat Grouping
| 9.BB.10 | Hardystonite | Ca2Zn[Si2O7] |
| 9.BB.10 | Jeffreyite | (Ca,Na)2(Be,Al)(Si2O7,HSi2O7) |
| 9.BB.10 | Alumoåkermanite | (CaNa)Al[Si2O7] |
| 9.BB.10 | Åkermanite | Ca2Mg[Si2O7] |
| 9.BB.10 | 'Ferri-gehlenite' | Ca2Fe3+[AlSiO7] |
| 9.BB.10 | Gehlenite | Ca2Al[AlSiO7] |
| 9.BB.10 | Ferroåkermanite | Ca2Fe[Si2O7] |
| 9.BB.10 | Cebollite | Ca5Al2(SiO4)3(OH)4 |
| 9.BB.10 | Hydroxylgugiaite | (Ca,◻)2(Si,Be)[(Be,Si)2O5.5(OH)1.5] |
| 9.BB.10 | Gugiaite | Ca2Be[Si2O7] |
| 9.BB.15 | Barylite | Be2Ba(Si2O7) |
| 9.BB.15 | 'Barylite-1O' | Be2Ba(Si2O7) |
| 9.BB.20 | Bennesherite | Ba2Fe2+[Si2O7] |
| 9.BB.20 | Andrémeyerite | BaFe2+2(Si2O7) |
Other Information
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 Okayamalite
mindat.org URL:
https://www.mindat.org/min-7202.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Okayamalite
Reference List:
Matsubara, Satoshi, Miyawaki, Ritsuro, Kato, Akira, Yokoyama, Kazumi, Okamoto, Akiyoshi (1998) Okayamalite, Ca2B2SiO7, a new mineral, boron analogue of gehlenite. Mineralogical Magazine, 62 (5) 703-706 doi:10.1180/002646198547936
Olmi, F., Viti, C., Bindi, L., Bonazzi, P., Menchetti, S. (2000) Second occurrence of okayamalite, Ca2SiB2O7: chemical and TEM characterization. American Mineralogist, 85 (10) 1508-1511 doi:10.2138/am-2000-1022
Localities for Okayamalite
Showing 2 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.
Japan (TL) | |
| Matsubara et al. (1998) |
Norway | |
| Olmi et al. (2000) +1 other reference |
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Fuka mine, Fuka, Bitchū, Takahashi City, Okayama Prefecture, Japan