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Brianroulstonite

A valid IMA mineral species
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Formula:
Ca3[B5O6(OH)6](OH)Cl2 · 8H2O
Colour:
Colorless to white.
Lustre:
Vitreous
Hardness:
5
Specific Gravity:
1.97
Crystal System:
Monoclinic
Name:
For Brian V. Roulston (1948-), geologist and evaporites specialist, in recognition of his work on the geology of evaporite deposits.
The OH analogue of popugaevaite.


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Unique IdentifiersHide

Mindat ID:
6834
Long-form identifier:
mindat:1:1:6834:1

IMA Classification of BrianroulstoniteHide

Classification of BrianroulstoniteHide

Strunz-mindat (2026):
6.EC.35

6 : BORATES
E : Pentaborates
C : Phyllo-pentaborates

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference for Standard
BrsnIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of BrianroulstoniteHide

Lustre:
Vitreous
Transparency:
Transparent, Translucent
Colour:
Colorless to white.
Streak:
White
Hardness:
5 on Mohs scale
Cleavage:
Perfect
{010}
Density:
1.97(3) g/cm3 (Measured)    1.93 g/cm3 (Calculated)

Optical Data of BrianroulstoniteHide

Type:
Biaxial (-)
RI values:
nα = 1.506(2) nβ = 1.527(2) nγ = 1.532(2)
2V:
Measured: 56° (1), Calculated: 51.4°
Max. Birefringence:
δ = 0.026
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.

Surface Relief:
Low (negative)
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.
Dispersion:
none

Chemistry of BrianroulstoniteHide

Mindat Formula:
Ca3[B5O6(OH)6](OH)Cl2 · 8H2O
Element Weights:
Element% weight
O55.594 %
Ca19.894 %
Cl11.732 %
B8.944 %
H3.836 %

Calculated from ideal end-member formula.
O
Ca
Cl
B
H
Elements listed:
B, Ca, Cl, H, O - search for minerals with similar chemistry

Crystallography of BrianroulstoniteHide

Crystal System:
Monoclinic
Class (H-M):
m - Domatic
Cell Parameters:
a = 17.367(4) Å, b = 8.079(2) Å, c = 8.693(2) Å
β = 121.56(2)°
Ratio:
a:b:c = 2.15 : 1 : 1.076
Unit Cell V:
1,039.30 ų (Calculated from Unit Cell)
Z:
2
Twinning:
About [102] on {010}, ubiquitous but observed only by X-ray diffraction.
Comment:
Space Group: Pa : pseudohexagonal

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0005524BrianroulstoniteGrice J D, Gault R A, Van Velthuizen J (1997) Brianroulstonite: A new borate mineral with a sheet structure The Canadian Mineralogist 35 751-75819970293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
8.10 Å(10)
4.04 Å(4)
3.56 Å(2)
2.834 Å(2)
2.535 Å(2)
2.276 Å(2)
7.06 Å(1)

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Near-surface Processes
25 : Evaporites (prebiotic)

Type Occurrence of BrianroulstoniteHide

Synonyms of BrianroulstoniteHide

Other Language Names for BrianroulstoniteHide

Related Minerals - Strunz-mindat GroupingHide

6.EC.CalcioveatchiteSrCaB11O16(OH)5 · 5H2OMon. 2 : P21
6.EC.05NasiniteNa2[B5O8(OH)] · 2H2OOrth. mmm(2/m2/m2/m)
6.EC.05BiringucciteNa2B5O8(OH) · H2OMon. 2/m : P21/b
6.EC.10GoweriteCa[B5O8(OH)][B(OH)3] · 3H2OMon. 2/m : P21/b
6.EC.15'Veatchite-2M'Sr2B11O16(OH)5 · H2OMon. m : Bb
6.EC.15'Veatchite-A'Sr2B11O16(OH)5 · H2OTric. 1 : P1
6.EC.15VeatchiteSr2B11O16(OH)5 · H2OMon. m : Bb
6.EC.15'Veatchite-1M'Sr2B11O16(OH)5 · H2OMon. 2 : P21
6.EC.20VolkovskiteKCa4[B5O8OH]4[B(OH)3]2Cl · 4H2OTric. 1 : P1
6.EC.25TuzlaiteNaCaB5O8(OH)2 · 3H2OMon. 2/m : P21/b
6.EC.30HeidorniteNa2Ca3B5O8(SO4)2Cl(OH)2Mon. 2/m : B2/b
6.EC.35PopugaevaiteCa3[B5O6(OH)6]FCl2 · 8H2OMon. m : Pm

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.

Internet Links for BrianroulstoniteHide

References for BrianroulstoniteHide

Localities for BrianroulstoniteHide

Showing 3 localities.

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.
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Locality ListHide

- 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). 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 (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
Canada (TL)
 
  • New Brunswick
    • Kings Co.
      • Cardwell Parish
        • Penobsquis
Grice et al. (1997) +2 other references
      • Hammond Parish
        • Salt Springs evaporite deposit
Burns et al. (1992)
Turkey
 
  • Eskişehir Province
    • Seyitgazi District
      • Kirka
Koçak et al. (2016) +1 other reference
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