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Mcallisterite
A valid IMA mineral species
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About Mcallisterite
J. F. McAllister
Formula:
Mg2[B6O7(OH)6]2 · 9H2O
Colour:
Colourless, white
Hardness:
2½
Specific Gravity:
1.867
Crystal System:
Trigonal
Name:
Named in 1965 by Waldemar Schaller, Angellina Calomeris Vlisidis, and Mary Emma Mrose in honor of James Franklin McAllister [November 11, 1911- September 29, 2000 Menlo Park, California, USA], USGS Geologist, who first described the material.
This page provides mineralogical data about Mcallisterite.
Unique Identifiers
Mindat ID:
2609
Long-form identifier:
mindat:1:1:2609:9
IMA Classification of Mcallisterite
Approved
IMA Formula:
Mg2[B6O7(OH)6]2·9H2O
Approval year:
1963
First published:
1965
Classification of Mcallisterite
6.FA.10
6 : BORATES
F : Hexaborates
A : Neso-hexaborates
6 : BORATES
F : Hexaborates
A : Neso-hexaborates
26.6.2.1
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
9.2.14
9 : Borates
2 : Borates of Be and Mg
9 : Borates
2 : Borates of Be and Mg
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 |
|---|---|---|
| Mcl | 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 Mcallisterite
Transparency:
Transparent
Colour:
Colourless, white
Streak:
White
Hardness:
2½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
on {0001} and {0112}
on {0001} and {0112}
Density:
1.867(5) g/cm3 (Measured) 1.866 g/cm3 (Calculated)
Optical Data of Mcallisterite
Type:
Uniaxial (-)
RI values:
nω = 1.504 nε = 1.459
Max. Birefringence:
δ = 0.045
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 (negative)
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 uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Chemistry of Mcallisterite
Mindat Formula:
Mg2[B6O7(OH)6]2 · 9H2O
Element Weights:
Elements listed:
Crystallography of Mcallisterite
Crystal System:
Trigonal
Class (H-M):
3m(32/m) - Hexagonal Scalenohedral
Space Group:
R3c
Setting:
R3c
Cell Parameters:
a = 11.546(1) Å, c = 35.562(5) Å
Ratio:
a:c = 1 : 3.08
Unit Cell V:
4,105.63 ų (Calculated from Unit Cell)
Z:
6
Morphology:
Rhombohedral crystals to 12 mm, efforescences .
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.715 Å | (100) |
| 5.772 Å | (50) |
| 4.063 Å | (50) |
| 3.351 Å | (50) |
| 3.261 Å | (50) |
| 2.805 Å | (50) |
| 6.645 Å | (35) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47c : [Carbonates, phosphates, borates, nitrates] |
Type Occurrence of Mcallisterite
General Appearance of Type Material:
Small pellets of clusters of crystals intimately intermixed with ginorite and sassolite. The pellets are typically 1-2 mm, rarely 1 cm. Individual crystals are less than 0.2 mm.
Place of Conservation of Type Material:
National School of Mines, Paris, France.
Harvard University, Cambridge, Massachusetts, USA, 109053.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, 134613, 162598.
Harvard University, Cambridge, Massachusetts, USA, 109053.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, 134613, 162598.
Geological Setting of Type Material:
Veins in basalt. Alteration of colemannite and priceite.
Associated Minerals at Type Locality:
Synonyms of Mcallisterite
Other Language Names for Mcallisterite
Common Associates
Associations Based on Photo Data:
| 1 photo of Mcallisterite associated with Starkeyite | MgSO4 · 4H2O |
| 1 photo of Mcallisterite associated with Gowerite | Ca[B5O8(OH)][B(OH)3] · 3H2O |
| 1 photo of Mcallisterite associated with Hexahydrite | Mg(H2O)6(SO4) |
Related Minerals - Strunz-mindat Grouping
| 6.FA.05 | Aksaite | Mg[B6O7(OH)6] · 2H2O |
| 6.FA.15 | Admontite | MgB6O10 · 7H2O |
| 6.FA.20 | Rivadavite | Na6Mg[B6O7(OH)6]4 · 10H2O |
| 6.FA.25 | Teruggite | Ca4Mg[AsO4]2[B6O7(OH)6]2 · 12H2O |
Fluorescence of Mcallisterite
Pale yellow
Other Information
Notes:
Slowly soluble in water.
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 Mcallisterite
mindat.org URL:
https://www.mindat.org/min-2609.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Mcallisterite
Reference List:
Allen, Robert D., Kramer, Henry (1957) Ginorite and sassolite from Death Valley, California. American Mineralogist, 42 (1-2) 56-61 (as an unknown)
Schaller, Waldemar T., Vlisidis, Angelina C., Mrose, and Mary E. (1965) Macallisterite, 2MgO·6B2O3·15H2O, a new hydrous magnesium borate mineral from the Death Valley region, Inyo County, California. American Mineralogist, 50 (5-6) 629-640
Localities for Mcallisterite
Showing 9 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.
Argentina | |
| Amer. Mineral. +5 other references |
China | |
| Shaoxiu (1991) +3 other references |
Kazakhstan | |
| Anatoly Kasatkin data |
USA | |
| Crowley (1996) +1 other reference |
| Erd et al. (1970) +1 other reference |
| Erd et al. (1979) |
| Schaller et al. (1965) +2 other references | |
| Erd et al. (1979) | |
| Dunn (1995) |
Quick NavTopAbout McallisteriteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatFluorescence Other InformationInternet Links References Localities Locality List
Sterling Mine, Sterling Hill, Ogdensburg, Sussex County, New Jersey, USA