Cairncrossite
A valid IMA mineral species
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About Cairncrossite
Professor Bruce Cairncross
Formula:
Sr2Ca7-xNa2x(Si4O10)4(OH)2(H2O)15-x
(with 0 ≤ x ≤ 1)
simplified formula of Na-rich crystals: SrCa3Na(Si4O10)2(OH)(H2O)7 (Z = 2).
simplified formula of Na-rich crystals: SrCa3Na(Si4O10)2(OH)(H2O)7 (Z = 2).
Colour:
Colourless
Lustre:
Vitreous, Pearly
Hardness:
3
Specific Gravity:
2.846 (Calculated)
Crystal System:
Triclinic
Member of:
Name:
Named after Professor Bruce Cairncross (born 13 August 1953), Emeritus Professor in the Department of Geology at the University of Johannesburg, Johannesburg, South Africa, in recognition of his work on the mineralogy of South Africa and especially its Mn deposits.
Belongs to both the Gyrolite and Reyerite groups. The combination of elements in the mineral is unique.
The structure is based on sheets of edge-sharing CaO6 octahedra. The sheets link by corners, on both sides, to silicate layers. Layers of paired edge-sharing SrO8 polyhedra are intercalated between the former units. The Sr polyhedra are further bound to disordered NaO6 polyhedra. Linkage to adjacent silicate layers is strenghtened by a complex system of hydrogen bonds.
The structure is based on sheets of edge-sharing CaO6 octahedra. The sheets link by corners, on both sides, to silicate layers. Layers of paired edge-sharing SrO8 polyhedra are intercalated between the former units. The Sr polyhedra are further bound to disordered NaO6 polyhedra. Linkage to adjacent silicate layers is strenghtened by a complex system of hydrogen bonds.
Unique Identifiers
Mindat ID:
43802
Long-form identifier:
mindat:1:1:43802:3
IMA Classification of Cairncrossite
Approved
Approval year:
2013
First published:
2016
Type description reference:
Giester, Gerald, Lengauer, Christian L., Pristacz, Helmut, Rieck, Branko, Topa, Dan, Von Bezing, Karl-Ludwig (2016) Cairncrossite, a new Ca-Sr (-Na) phyllosilicate from the Wessels Mine, Kalahari Manganese Field, South Africa. European Journal of Mineralogy, 28 (2) 495-505 doi:10.1127/ejm/2016/0028-2519
Classification of Cairncrossite
9.EE.
9 : SILICATES (Germanates)
E : Phyllosilicates
E : Single tetrahedral nets of 6-membered rings connected by octahedral nets or octahedral bands
9 : SILICATES (Germanates)
E : Phyllosilicates
E : Single tetrahedral nets of 6-membered rings connected by octahedral nets or octahedral bands
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Ccs | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Ccs | Warr (2020) | Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261–264 doi:10.1180/clm.2020.30 |
Physical Properties of Cairncrossite
Vitreous, Pearly
Transparency:
Transparent, Translucent
Colour:
Colourless
Comment:
Appears white
Streak:
White
Hardness:
3 on Mohs scale
Tenacity:
Sectile
Cleavage:
Perfect
Parallel to (001)
Parallel to (001)
Comment:
"sectile before brittle fracture"
Density:
2.846 g/cm3 (Calculated)
Optical Data of Cairncrossite
Type:
Biaxial (+)
RI values:
nα = 1.518(2) nβ = 1.522(2) nγ = 1.546(2)
2V:
Measured: 33.9° (6), Calculated: 44.97°
Max. Birefringence:
δ = 0.028
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:
None to Very Low
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 (r < v)
Pleochroism:
Non-pleochroic
Comments:
indicatrix orientation: Z ∧ c* = 10°
Chemistry of Cairncrossite
Mindat Formula:
Sr2Ca7-xNa2x(Si4O10)4(OH)2(H2O)15-x
(with 0 ≤ x ≤ 1)
simplified formula of Na-rich crystals: SrCa3Na(Si4O10)2(OH)(H2O)7 (Z = 2).
(with 0 ≤ x ≤ 1)
simplified formula of Na-rich crystals: SrCa3Na(Si4O10)2(OH)(H2O)7 (Z = 2).
Element Weights:
Common Impurities:
Na
Crystallography of Cairncrossite
Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 9.6265(5) Å, b = 9.6391(5) Å, c = 15.6534(10) Å
α = 100.89(1)°, β = 91.27(1)°, γ = 119.73(1)°
α = 100.89(1)°, β = 91.27(1)°, γ = 119.73(1)°
Ratio:
a:b:c = 0.999 : 1 : 1.624
Unit Cell V:
1227.08 ų
Z:
1
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 15.230 Å | (100) |
| 3.807 Å | (30) |
| 5.080 Å | (25) |
| 3.045 Å | (20) |
Reference:
Giester, Gerald, Lengauer, Christian L., Pristacz, Helmut, Rieck, Branko, Topa, Dan, Von Bezing, Karl-Ludwig (2016) Cairncrossite, a new Ca-Sr (-Na) phyllosilicate from the Wessels Mine, Kalahari Manganese Field, South Africa. European Journal of Mineralogy, 28 (2) 495-505 doi:10.1127/ejm/2016/0028-2519
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits |
Type Occurrence of Cairncrossite
General Appearance of Type Material:
Radiating platy-micaceous aggregates, up to 1 cm.
Place of Conservation of Type Material:
In the collections of the Institute of Mineralogy and Crystallography, University of Vienna, Vienna, Austria, registration number 13079.
Geological Setting of Type Material:
Dump material (within Mn ore). The last mineral to have formed during metasomatic alteration of a primary carbonate-rich manganese ore.
Associated Minerals at Type Locality:
Reference:
Giester, Gerald, Lengauer, Christian L., Pristacz, Helmut, Rieck, Branko, Topa, Dan, Von Bezing, Karl-Ludwig (2016) Cairncrossite, a new Ca-Sr (-Na) phyllosilicate from the Wessels Mine, Kalahari Manganese Field, South Africa. European Journal of Mineralogy, 28 (2) 495-505 doi:10.1127/ejm/2016/0028-2519
Synonyms of Cairncrossite
Other Language Names for Cairncrossite
Dutch:Cairncrossiet
German:Cairncrossit
Relationship of Cairncrossite to other Species
Member of:
Other Members of Gyrolite Group:
| Gyrolite | NaCa16Si23AlO60(OH)8 · 14H2O | Tric. 1 : P1 |
| Orlymanite | Ca4Mn3Si8O20(OH)6 · 2H2O | Hex. |
| Tungusite | Ca4Fe2Si6O15(OH)6 | Tric. 1 : P1 |
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 9.EE.05 | Bementite | Mn7Si6O15(OH)8 |
| 9.EE.07 | Innsbruckite | Mn33(Si2O5)14(OH)38 |
| 9.EE.10 | 'Brokenhillite' | Mn8Si6O15(OH)10 |
| 9.EE.10 | Mcgillite | (Mn,Fe)8Si6O15(OH)8Cl2 |
| 9.EE.10 | Friedelite | Mn2+8Si6O15(OH,Cl)10 |
| 9.EE.10 | Pyrosmalite-(Mn) | Mn2+8Si6O15(OH,Cl)10 |
| 9.EE.10 | Pyrosmalite-(Fe) | Fe2+8Si6O15(OH,Cl)10 |
| 9.EE.15 | Nelenite | Mn2+16As3+3Si12O36(OH)17 |
| 9.EE.15 | Schallerite | Mn2+16As3Si12O36(OH)17 |
| 9.EE.20 | Palygorskite | ◻Al2Mg2◻2Si8O20(OH)2(H2O)4 · 4H2O |
| 9.EE.20 | Yofortierite | Mn2+Mn2+2Mn2+2◻2Si8O20(OH)2(H2O)4 · 4H2O |
| 9.EE.20 | Windhoekite | Fe3+(Fe3+1.67◻0.33)Ca2◻2Si8O20(OH)2(H2O)4(OH)2 · 6H2O |
| 9.EE.20 | Windmountainite | ◻Fe3+2Mg2◻2Si8O20(OH)2(H2O)4 · 4H2O |
| 9.EE.20 | Ikorskyite | KMn3+(Si4O10) · 3H2O |
| 9.EE.20 | Tuperssuatsiaite | Fe3+Fe3+2(Na◻)◻2Si8O20(OH)2(H2O)4 · 2H2O |
| 9.EE.20 | 'Unnamed (Na-Ca-Fe-Silicate-Hydrate)' | NaCa(Fe2+,Al,Mn)5[Si8O19(OH)](OH)7 · 5H2O |
| 9.EE.25 | Sepiolite | Mg4(Si6O15)(OH)2 · 6H2O |
| 9.EE.25 | Loughlinite | Na2Mg3Si6O16 · 8H2O |
| 9.EE.25 | Falcondoite | (Ni,Mg)4Si6O15(OH)2 · 6H2O |
| 9.EE.25 | Kalifersite | (K,Na)5Fe3+7Si20O50(OH)6 · 12H2O |
| 9.EE.30 | Orlymanite | Ca4Mn3Si8O20(OH)6 · 2H2O |
| 9.EE.30 | Tungusite | Ca4Fe2Si6O15(OH)6 |
| 9.EE.30 | Gyrolite | NaCa16Si23AlO60(OH)8 · 14H2O |
| 9.EE.35 | Reyerite | (Na,K)2Ca14(Si,Al)24O58(OH)8 · 6H2O |
| 9.EE.35 | Kodamaite | Na3(Ca5Na)Si16O36(OH)4F2 · (14-x)H2O |
| 9.EE.35 | Truscottite | (Ca,Mn)14Si24O58(OH)8 · 2H2O |
| 9.EE.40 | Natrosilite | Na2Si2O5 |
| 9.EE.45 | Makatite | Na2Si4O8(OH)2 · 4H2O |
| 9.EE.50 | Varennesite | Na8Mn2Si10O25(OH,Cl)2 · 12H2O |
| 9.EE.55 | Raite | Mn2+Mn2+2Na2(◻1.75Ti0.25)Si8O20(OH)2(H2O)4 · Na(H2O)6 |
| 9.EE.60 | Intersilite | Na6Mn2+Ti[Si10O24(OH)](OH)3 · 4H2O |
| 9.EE.65 | Zakharovite | Na4Mn5Si10O24(OH)6 · 6H2O |
| 9.EE.65 | Shafranovskite | Na3K2(Mn,Fe,Na)4[Si9(O,OH)27](OH)2 · nH2O |
| 9.EE.70 | Zeophyllite | Ca13Si10O28(OH)2F8 · 6H2O |
| 9.EE.75 | Minehillite | (K,Na)2-3Ca28Zn4Al4Si40O112(OH)16 |
| 9.EE.80 | Fedorite | (Na,K)2-3(Ca4Na3)Si16O38(OH,F)2 · 3.5H2O |
| 9.EE.80 | Martinite | (Na,◻,Ca)12Ca4(Si,S,B)14B2O38(OH,Cl)2F2 · 4H2O |
| 9.EE.80 | Ellingsenite | Na5Ca6Si18O38(OH)13 · 6H2O |
| 9.EE.85 | Lalondeite | (Na,Ca)6(Ca,Na)3Si16O38(F,OH)2 · 3H2O |
Fluorescence of Cairncrossite
light-blue, intense (SWUV)
Other Information
Thermal Behaviour:
25–400oC: two-phase endothermic weight loss of water vs nearly complete rehydration capability up to 400oC
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 Cairncrossite
mindat.org URL:
https://www.mindat.org/min-43802.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 Cairncrossite
Reference List:
Williams, P. A., Hatert, F., Pasero, M., Mills, S. J. (2013) New minerals and nomenclature modifications approved in 2013. CNMNC Newsletter No 16. Mineralogical Magazine, 77 (6) 2695-2709 doi:10.1180/minmag.2013.077.6.01
Giester, Gerald, Lengauer, Christian L., Pristacz, Helmut, Rieck, Branko, Topa, Dan, Von Bezing, Karl-Ludwig (2016) Cairncrossite, a new Ca-Sr (-Na) phyllosilicate from the Wessels Mine, Kalahari Manganese Field, South Africa. European Journal of Mineralogy, 28 (2) 495-505 doi:10.1127/ejm/2016/0028-2519
Localities for Cairncrossite
Showing 1 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.
South Africa (TL) | |
| Williams et al. (2013) +1 other reference |
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Wessels Mine, Joe Morolong Local Municipality, John Taolo Gaetsewe District Municipality, Northern Cape, South Africa