Cahnite
A valid IMA mineral species - grandfathered
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About Cahnite
Lazard Cahn
Formula:
Ca2[B(OH)4](AsO4)
Colour:
Colorless to white, golden brown
Lustre:
Vitreous, Sub-Vitreous, Resinous
Hardness:
3
Specific Gravity:
3.156
Crystal System:
Tetragonal
Name:
Named in 1921 by Charles Palache, but not described until 1927 by Charles Palache and Lawson Henry Bauer in honor of Mr. Lazard Cahn [May 23, 1865 Saint Joseph, Missouri, USA - May 22, 1940 Colorado Springs, Colorado, USA] morphological crystallographer, mineral collector and mineral dealer, who first recognized the material.
Type Locality:
Unique Identifiers
Mindat ID:
851
Long-form identifier:
mindat:1:1:851:2
Similar Names
| Conite (of Macculloch) | A synonym of Quartz | |
| Conite (of Schumacher) | A synonym of 'Mg-rich Dolomite' | |
| Gahnite | A valid IMA mineral species - grandfathered | ZnAl2O4 |
| Gahnite (of Lobo da Silveira) | A synonym of Vesuvianite | |
| Gainite | A synonym of Hainite-(Y) | |
| Guanite | A synonym of Struvite | |
| Kainite | A valid IMA mineral species - grandfathered | KMg(SO4)Cl · 3H2O |
| Kaneite | MnAs | |
| Kanoite | A valid IMA mineral species | Mn2+MgSi2O6 |
| Kühnite | A synonym of Berzeliite |
IMA Classification of Cahnite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ca2B(As5+O4)(OH)4
First published:
1927
Classification of Cahnite
6.AC.70
6 : BORATES
A : Monoborates
C : B(O,OH)4, without and with additional anions; 1(T), 1(T)+OH, etc
6 : BORATES
A : Monoborates
C : B(O,OH)4, without and with additional anions; 1(T), 1(T)+OH, etc
43.4.4.1
43 : COMPOUND PHOSPHATES, ETC.
4 : Anhydrous Compound Phosphates, etc·, Containing Hydroxyl or Halogen
43 : COMPOUND PHOSPHATES, ETC.
4 : Anhydrous Compound Phosphates, etc·, Containing Hydroxyl or Halogen
10.2.2
10 : Borates with other anions
2 : Borates with phosphate or arsenate
10 : Borates with other anions
2 : Borates with phosphate or arsenate
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 |
|---|---|---|
| Cah | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Pronunciation of Cahnite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Cahnite
Vitreous, Sub-Vitreous, Resinous
Transparency:
Transparent, Translucent
Colour:
Colorless to white, golden brown
Comment:
Colourless in transmitted light.
Streak:
White
Hardness:
3 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
On {110}
On {110}
Fracture:
Irregular/Uneven, Sub-Conchoidal
Density:
3.156 g/cm3 (Measured) 3.22 g/cm3 (Calculated)
Optical Data of Cahnite
Type:
Uniaxial (+)
RI values:
nω = 1.655 - 1.662 nε = 1.656 - 1.663
Birefringence:
0.001
Max. Birefringence:
δ = 0.001
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 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.
Dispersion:
Strong; exhibits anomalous interference colors.
Pleochroism:
Non-pleochroic
Comments:
Exhibits abnormal interference colours that make the mineral easily recognizable under the microscope.
Chemistry of Cahnite
Mindat Formula:
Ca2[B(OH)4](AsO4)
Element Weights:
Crystallography of Cahnite
Crystal System:
Tetragonal
Class (H-M):
4 - Disphenoidal
Space Group:
P4
Cell Parameters:
a = 7.09 Å, c = 6.19 Å
Ratio:
a:c = 1 : 0.873
Unit Cell V:
311.16 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Single untwinned crystals rare, pseudo-tetrahedral habit.
Twinning:
Almost universal on {110}, with the individuals interpenetrating symmetrically. When the sphenoid faces are well-developed, the twins have a characteristic cruciform appearance.
Crystal Structure
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Unit Cell | Unit Cell Packed
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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) |
|---|---|---|---|---|---|---|---|
| 0000097 | Cahnite | Prewitt C T, Buerger M J (1961) The crystal structure of cahnite, Ca2BAsO4(OH)4 American Mineralogist 46 1077-1085 |  | 1961 | Franklin, New Jersey, USA | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 5.02 Å | (20) |
| 4.67 Å | (20) |
| 3.56 Å | (100) |
| 2.833 Å | (19) |
| 2.640 Å | (48) |
| 2.336 Å | (17) |
| 1.818 Å | (52) |
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) | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks | |
| Stage 7: Great Oxidation Event | <2.4 |
| 46 : Near-surface hydrothermal alteration of minerals (see also #22) |
Geological Setting:
cavities in boron-bearing and arsenate-bearing vugs in basalt, boron-bearing and arsenate-bearing hydrothermal veins
Type Occurrence of Cahnite
General Appearance of Type Material:
Tiny white glassy crystals, characteristically twinned with generally etched crystal faces.
Place of Conservation of Type Material:
Harvard University, Cambridge, Massachusetts, USA, numbers 90010, 90015, 90016, 90019.
National Museum of Natural History, Washington, D.C., USA, number 95568.
National Museum of Natural History, Washington, D.C., USA, number 95568.
Geological Setting of Type Material:
Cavities in manganaxinite veinlets traversing Precambrian metamorphosed Zn-Mn-Fe orebody.
Associated Minerals at Type Locality:
Synonyms of Cahnite
Other Language Names for Cahnite
Common Associates
Associations Based on Photo Data:
| 75 photos of Cahnite associated with Borcarite | Ca4Mg(B4O6(OH)6)(CO3)2 |
| 25 photos of Cahnite associated with Rhodonite | CaMn3Mn[Si5O15] |
| 12 photos of Cahnite associated with Axinite-(Mn) | Ca2Mn2+Al2BSi4O15(OH) |
| 8 photos of Cahnite associated with Andradite | Ca3Fe3+2(SiO4)3 |
| 8 photos of Cahnite associated with Willemite | Zn2SiO4 |
| 7 photos of Cahnite associated with Ganophyllite | (K,Na)xMn2+6(Si,Al)10O24(OH)4 · nH2O (x = 1-2; n = 7-11) |
| 7 photos of Cahnite associated with Flinkite | Mn2+2Mn3+(AsO4)(OH)4 |
| 6 photos of Cahnite associated with Calcite | CaCO3 |
| 6 photos of Cahnite associated with Bementite | Mn7Si6O15(OH)8 |
| 6 photos of Cahnite associated with Hancockite | (CaPb)(AlAlFe3+)O[Si2O7][SiO4](OH) |
Related Minerals - Strunz-mindat Grouping
| 6.AC.05 | Sinhalite | MgAl(BO4) |
| 6.AC.10 | Pseudosinhalite | Mg2Al3(BO3)2(OH)O3 |
| 6.AC.15 | Béhierite | Ta(BO4) |
| 6.AC.15 | Schiavinatoite | Nb(BO4) |
| 6.AC.20 | Frolovite | Ca[B(OH)4]2 |
| 6.AC.25 | Hexahydroborite | Ca[B(OH)4]2 · 2H2O or CaB2O4 · 6H2O |
| 6.AC.30 | Henmilite | Ca2Cu[B(OH)4]2(OH)4 |
| 6.AC.35 | Bandylite | Cu[B(OH)4]Cl |
| 6.AC.40 | Teepleite | Na2[B(OH)4]Cl |
| 6.AC.45 | Moydite-(Y) | Y[B(OH)4](CO3) |
| 6.AC.50 | Carboborite | Ca2Mg[B(OH)4]2(CO3)2 · 4H2O |
| 6.AC.55 | Sulfoborite | Mg3[B(OH)4]2(SO4)(OH,F)2 |
| 6.AC.60 | Lüneburgite | Mg3[B2(OH)6](PO4)2 · 6H2O |
| 6.AC.65 | Seamanite | Mn2+3[B(OH)4](PO4)(OH)2 |
Fluorescence of Cahnite
Fluoresces moderate creamy white in SW UV (Franklin).
Other Information
Notes:
Readily soluble in dilute HCl.
Fuses quietly at about 3 yielding the green flame of boron. In the closed tube, heated alone it yields water and becomes opaque but does not fuse; heated with potassium carbonate and carbon it yields an arsenic mirror.
Fuses quietly at about 3 yielding the green flame of boron. In the closed tube, heated alone it yields water and becomes opaque but does not fuse; heated with potassium carbonate and carbon it yields an arsenic mirror.
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 Cahnite
mindat.org URL:
https://www.mindat.org/min-851.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 Cahnite
Reference List:
Palache, Charles, Bauer, L. H. (1927) Cahnite, a new boro-arsenate of calcium from Franklin, New Jersey. American Mineralogist, 12 (4) 149-153
Palache, Charles (1941) Crystallographic notes: cahnite, stolzite, zincite, ultrabasite. American Mineralogist, 26 (7) 429-436
Embrey, P. G. (1960) Cahnite from Capo di Bove, Rome. Mineralogical Magazine and Journal of the Mineralogical Society, 32 (251) 666-668 doi:10.1180/minmag.1960.032.251.10
Prewitt, Charles T., Buerger, M. J. (1961) The crystal structure of cahnite, Ca2BAsO4(OH)4. American Mineralogist, 46 (9-10 ) 1077-1085
Localities for Cahnite
Showing 16 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.
Brazil | |
| Orris et al. (2002) |
Chile | |
| TESIS PARA OPTAR AL GRADO DE MAGÍSTER ... |
China | |
| Ottens et al. (2012) |
| Ottens et al. (2014) | |
Italy | |
| Embrey (1960) |
| Stoppani et al. (1982) +2 other references |
Japan | |
| Shiraga et al. (2002) |
Mexico | |
| Peter Megaw collection |
| Peter Megaw collection | |
| Miranda-Gasca et al. (1998) +1 other reference |
Namibia | |
| Bode Verlag GmbH et al. (in English) +2 other references |
Norway | |
| Bugge (1951) |
Russia | |
| Doklady Acad. Nauk SSSR 166 (1966) |
Turkey | |
| American Mineralogist +7 other references |
| American Mineralogist +4 other references | |
USA (TL) | |
| Palache et al. (1927) +3 other references |
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Franklin Mine, Franklin, Sussex County, New Jersey, USA