Gearksutite
A valid IMA mineral species - grandfathered
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About Gearksutite
Formula:
Ca[Al(F,OH)5(H2O)]
Colour:
white, pale rose, colourless (including in transmitted light)
Lustre:
Dull
Hardness:
2
Specific Gravity:
2.768
Crystal System:
Triclinic
Name:
From the Greek γή, earth, and arksutite (chiolite), which it was thought to resemble in composition, in allusion to the earthy character of the material.
Unique Identifiers
Mindat ID:
1663
Long-form identifier:
mindat:1:1:1663:2
IMA Classification of Gearksutite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
CaAlF4(OH)·H2O
Classification of Gearksutite
3.CC.05
3 : HALIDES
C : Complex halides
C : Soro-aluminofluorides
3 : HALIDES
C : Complex halides
C : Soro-aluminofluorides
11.6.8.1
11 : HALIDE COMPLEXES
6 : Aluminofluorides - Isolated Octahedra
11 : HALIDE COMPLEXES
6 : Aluminofluorides - Isolated Octahedra
8.6.12
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
6 : Halides of Al
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
6 : Halides of Al
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 |
|---|---|---|
| Gak | 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 Gearksutite
Dull
Transparency:
Transparent, Opaque
Colour:
White, pale rose, colourless (including in transmitted light)
Comment:
transparent in thin fibers
Streak:
White
Hardness:
2 on Mohs scale
Cleavage:
Imperfect/Fair
On {110}.
On {110}.
Density:
2.768 g/cm3 (Measured) 2.771 g/cm3 (Calculated)
Optical Data of Gearksutite
Type:
Biaxial (-)
RI values:
nα = 1.448 nβ = 1.454 nγ = 1.456
Max. Birefringence:
δ = 0.008
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:
High (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 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.
No measured or calculated 2V is on file for this mineral, so the value used here (60°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
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.
No measured or calculated 2V is on file for this mineral, so the value used here (60°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
r > v distinct
Chemistry of Gearksutite
Mindat Formula:
Ca[Al(F,OH)5(H2O)]
Element Weights:
Crystallography of Gearksutite
Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 4.940(1) Å, b = 6.810(1) Å, c = 6.978(1) Å
α = 101.12°, β = 94.86°, γ = 110.07°
α = 101.12°, β = 94.86°, γ = 110.07°
Ratio:
a:b:c = 0.725 : 1 : 1.025
Unit Cell V:
213.43 ų
Z:
2
Morphology:
Massive; nodular with an earthy to chalky character. Consisting of very minute needles with inclined extinction.
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Polyhedra Off | Si Polyhedra | All Polyhedra
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Display Options
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View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
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Labels
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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) |
|---|---|---|---|---|---|---|---|
| 0002346 | Gearksutite | Marchetti F, Perchiazzi N (2000) The crystal structure of gearksutite, CaAlF4(OH).H2O American Mineralogist 85 231-235 |  | 2000 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Loading XRD data...
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.54 Å | (10) |
| 3.33 Å | (7d) |
| 3.14 Å | (8) |
| 2.28 Å | (8) |
| 2.15 Å | (6) |
| 1.924 Å | (8) |
| 1.741 Å | (6) |
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 |
| 34 : Complex granite pegmatites | |
| Stage 7: Great Oxidation Event | <2.4 |
| 45b : [Other oxidized fumarolic minerals] |
Type Occurrence of Gearksutite
Synonyms of Gearksutite
Other Language Names for Gearksutite
Dutch:Gearksutiet
German:Gearksutit
Russian:Геарксутит
Simplified Chinese:氟铝钙矿
Spanish:Gearksutita
Traditional Chinese:氟鋁鈣礦
Common Associates
Associations Based on Photo Data:
| 25 photos of Gearksutite associated with Creedite | Ca3Al2(SO4)(OH)2F8 · 2H2O |
| 16 photos of Gearksutite associated with Fluorite | CaF2 |
| 15 photos of Gearksutite associated with Quartz | SiO2 |
| 10 photos of Gearksutite associated with Prosopite | CaAl2F4[(OH)4-xFx] |
| 8 photos of Gearksutite associated with Linarite | PbCu(SO4)(OH)2 |
| 6 photos of Gearksutite associated with Weberite | Na2Mg[AlF6]F |
| 4 photos of Gearksutite associated with Gypsum | CaSO4 · 2H2O |
| 4 photos of Gearksutite associated with Cerussite | PbCO3 |
| 3 photos of Gearksutite associated with Siderite | FeCO3 |
| 3 photos of Gearksutite associated with Serpierite | Ca(Cu2+,Zn2+)4(S6+O4)2(OH)6 · 3H2O |
Related Minerals - Strunz-mindat Grouping
| 3.CC.10 | Acuminite | Sr[AlF4(OH)(H2O)] |
| 3.CC.10 | Tikhonenkovite | Sr[AlF4(OH)(H2O)] |
| 3.CC.15 | Artroeite | Pb[AlF3(OH)2] |
| 3.CC.20 | Jarlite | Na(Sr,Na)7MgAl6F32(OH,H2O)2 |
| 3.CC.20 | Calcjarlite | Na(Ca,Sr)3Al3(OH)2F14 |
| 3.CC.20 | Jørgensenite | Na2(Sr,Ba)14Na2Al12F64(OH,F)4 |
Fluorescence of Gearksutite
Compact, massive material fluoresces dark violet to bluish gray; powdery material fluoresces yellowish brown.
Other Information
Notes:
Readily soluble in dilute acid.
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 Gearksutite
mindat.org URL:
https://www.mindat.org/min-1663.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 Gearksutite
Reference List:
Cross, W.; Hillebrand, W.F. (1885) Contributions to the mineralogy of the Rocky Mountains. Bulletin 20. US Geological Survey 114 pp. doi:10.3133/b20 p.59
Bøggild, O.B. (1912) Iagttagelser over Kryolitgruppens Mineraler [Observations on the Minerals of the Cryolite Group]. Meddelelser om Grønland, 50 (3).
Simpson, E.S. (1920) On Gearksutite at Gingin, Western Australia. Mineralogical Magazine: 19: 23-39.
Larsen, Esper S. (1921) The microscopic determination of the nonopaque minerals. Bulletin 679. US Geological Survey doi:10.3133/b679 p.78
Fleischer, M., Rooseboom, E. H., Skinner, Brian (1960) New Mineral Names; New data; Discredited minerals. American Mineralogist, 45 (9-10) 1130-1136
(1962) International Mineralogical Association: Commission on New Minerals and Mineral Names. Mineralogical Magazine and Journal of the Mineralogical Society, 33 (258) 260-263 doi:10.1180/minmag.1962.033.258.09
Ziborova, T. A.; Fin'ko, V. I.; Basalayeva, I. V.; Samotoin, N. D. (1986) Some crystallochemical features of gearksutite. International Geology Review, 28 (11). 1369-1373 doi:10.1080/00206818609466373
Marchetti, Fabio, Perchiazzi, Natale (2000) The crystal structure of gearksutite, CaAlF4(OH)·H2O. American Mineralogist, 85 (1) 231-235 doi:10.2138/am-2000-0123
Localities for Gearksutite
Showing 90 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.
Australia | |
| Am Min 85:231-235 +1 other reference |
| Edward S. Simpson (1920) +1 other reference |
Austria | |
| Program and Abstracts Volume +2 other references |
| Kolitsch (2016) |
Bolivia | |
| Walenta et al. (1980) +1 other reference |
Brazil | |
| JENKINS II (1987) |
China | |
| Niedermayr (2004) |
| Mingyue He et al. (2002) |
Finland | |
| Ilkka Mikkola collection |
France | |
| Pascal Chollet collection |
Germany | |
| 58 +5 other references |
| Gröbner et al. (2011) |
| Möhn et al. (07/2020) |
Greece | |
| |
| Wendel (2000) +2 other references | |
| Kolitsch et al. (2014) |
| Rieck (n.d.) |
Greenland (TL) | |
| Palache et al. (1951) +2 other references |
Italy | |
| Russo et al. (2014) +1 other reference |
| Russo et al. (2011) +2 other references |
| Campostrini et al. (2019) | |
| Russo et al. (2014) +1 other reference | |
| Bortolozzi et al. (2018) |
| Prof. P. Orlandi personal communication ... |
| Bernauer (1941) |
| Campostrini et al. (2011) | |
| Bernauer (1941) +2 other references | |
| Bortolozzi et al. (2021) |
| - (n.d.) |
| Biagioni et al. (2013) |
| Biagioni et al. (2013) | |
| Menchetti et al. (2015) |
| Boscardin M. et al. (1995) +1 other reference |
| American Mineralogist | |
| Pegoraro S. (2014) | |
| Neschen (n.d.) |
Kazakhstan | |
| Pavel M. Kartashov (n.d.) +1 other reference |
| Evseev (1995) +2 other references |
| Pavel M. Kartashov (n.d.) |
Kyrgyzstan | |
| Kolesar et al. (1993) |
Mexico | |
| Megaw (2023) |
| Panczner (1987) |
Norway | |
| Dietrich et al. (1965) +1 other reference |
Russia | |
| Bailey (1980) |
| Arkhipchuk (1971) | |
| Ripp et al. (1996) +1 other reference |
| webmineral.ru (2016) |
| M.M. Povilaitis data (http://klopotow.narod.ru/mindata/locathn/R_Buryat/zakamensk/djida.html) | |
| Bailey (1980) +1 other reference |
| Raade et al. (1980) | |
| Pekov et al. (2025) +1 other reference |
| Pekov (1998) |
| Pekov (1998) |
| Bailey (1980) |
| Pavel M. Kartashov (n.d.) +1 other reference | |
| Pavel M. Kartashov (n.d.) |
| P.M. Karashov data |
South Africa | |
| Cairncross et al. (1995) +1 other reference |
| Robert O. Meyer collection +2 other references |
Spain | |
| Calvo Rebollar (2006) |
| Rodríguez +3 other references |
| Rosell et al. (2017) |
UK | |
| Norman Wilson collection |
| Norman Wilson personal collection |
Ukraine | |
| Yurk Yu.Yu. et al. (1973) +1 other reference |
USA | |
| Rob Bowell |
| Rob Bowell | |
| Jones (1980) +1 other reference |
| Eckel et al. (1997) |
| Eckel et al. (1997) | |
| Eckel et al. (1997) |
| Palache et al. (1951) +1 other reference |
| Gross et al. (1966) | |
| Pavel M. Kartashov analytical data (2012) | |
| Gross et al. (1966) | |
| Eckel et al. (1997) |
| Palache et al. (1951) +1 other reference |
| 2009 New Mexico Mineral Symposium ... +1 other reference |
| Castor et al. (2004) |
| Walstrom (n.d.) +1 other reference |
| Castor et al. (2004) |
| Castor et al. (2004) |
| Castor et al. (2004) |
| Bullock (1981) |
| Bullock (1981) |
| Bullock (1981) |
| Kearns et al. (2000) |
| The System of Mineralogy of James ... +3 other references |
| Lasmanis (1983) |
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Uranus Mine, Kleinrückerswalde, Annaberg-Buchholz, Erzgebirgskreis, Saxony, Germany