Leightonite
A valid IMA mineral species - grandfathered
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About Leightonite
Formula:
K2Ca2Cu(SO4)4 · 2H2O
Colour:
Pale blue, greenish-blue; pale blue in transmitted light.
Lustre:
Vitreous
Hardness:
3
Specific Gravity:
2.95
Crystal System:
Monoclinic
Name:
Named in honor of Tomás Leighton Donoso (1896–1967), Professor of Mineralogy, University of Santiago, Chile.
Unique Identifiers
Mindat ID:
2369
Long-form identifier:
mindat:1:1:2369:2
IMA Classification of Leightonite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
K2Ca2Cu2+(S6+O4)4(H2O)2
First published:
1938
Classification of Leightonite
7.CC.70
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
C : With medium-sized and large cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
C : With medium-sized and large cations
29.4.5.2
29 : HYDRATED ACID AND NORMAL SULFATES
4 : AmBn(XO4)p·xH2O, with (m+n):p < 3:2 and > 1:1
29 : HYDRATED ACID AND NORMAL SULFATES
4 : AmBn(XO4)p·xH2O, with (m+n):p < 3:2 and > 1:1
25.2.18
25 : Sulphates
2 : Sulphates of Cu and Ag
25 : Sulphates
2 : Sulphates of Cu and Ag
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 |
|---|---|---|
| Lgh | 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 Leightonite
Vitreous
Transparency:
Transparent, Translucent
Colour:
Pale blue, greenish-blue; pale blue in transmitted light.
Hardness:
3 on Mohs scale
Cleavage:
None Observed
Density:
2.95 g/cm3 (Measured) 2.95 g/cm3 (Calculated)
Optical Data of Leightonite
Type:
Biaxial (-)
RI values:
nα = 1.574 - 1.578 nβ = 1.587 nγ = 1.595
2V:
Measured: 60° , Calculated: 86°
Max. Birefringence:
δ = 0.017 - 0.021
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 (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 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:
very weak
Chemistry of Leightonite
Mindat Formula:
K2Ca2Cu(SO4)4 · 2H2O
Element Weights:
Crystallography of Leightonite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Setting:
C2/c
Cell Parameters:
a = 11.654(2) Å, b = 7.497(1) Å, c = 10.097(1) Å
β = 125.21(1)°
β = 125.21(1)°
Ratio:
a:b:c = 1.554 : 1 : 1.347
Unit Cell V:
720.78 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Pseudo-orthorhombic. Blades or laths elongated [001] and flattened {100}; rarely equant. Curved surfaces cutting away more or less of the front edges of the prism produce an hour-glass appearance. Also occurs as cross-fiber veinlets.
Twinning:
Repeated lamellar twinning on (100) and (010) of a sub-rectangular triclinic structure results in mimetic orthorhombic symmetry.
Crystal Structure
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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) |
|---|---|---|---|---|---|---|---|
| 0002814 | Leightonite | Menchetti S, Bindi L, Bonazzi P, Olmi F (2002) Disordered distribution of Cu in the crystal structure of leightonite, K2Ca2Cu(SO4)4.2H2O American Mineralogist 87 721-725 |  | 2002 | 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 |
|---|---|
| 2.90 Å | (100) |
| 3.18 Å | (60) |
| 1.781 Å | (30) |
| 2.22 Å | (20) |
| 2.51 Å | (10) |
| 2.40 Å | (10) |
| 1.461 Å | (10) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] |
Type Occurrence of Leightonite
General Appearance of Type Material:
cross-fiber veinlet fillings and crystals in open cavities.
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1938,56.
Harvard University, Cambridge, Massachusetts, 97540–97544.
National Museum of Natural History, Washington, D.C., USA, C5536.
Harvard University, Cambridge, Massachusetts, 97540–97544.
National Museum of Natural History, Washington, D.C., USA, C5536.
Associated Minerals at Type Locality:
Other Language Names for Leightonite
Common Associates
Associations Based on Photo Data:
| 9 photos of Leightonite associated with Natrochalcite | NaCu2(SO4)2(OH) · 2H2O |
| 6 photos of Leightonite associated with Paratacamite | Cu3(Cu,Zn)(OH)6Cl2 |
| 3 photos of Leightonite associated with Atacamite | Cu2(OH)3Cl |
| 3 photos of Leightonite associated with Bellingerite | Cu3(IO3)6 · 2H2O |
| 2 photos of Leightonite associated with Marshite | CuI |
| 1 photo of Leightonite associated with Antlerite | Cu3(SO4)(OH)4 |
Related Minerals - Strunz-mindat Grouping
| 7.CC. | Cobaltoblödite | Na2Co(SO4)2 · 4H2O |
| 7.CC. | Andychristyite | PbCu2+Te6+O5(H2O) |
| 7.CC. | Ammoniovoltaite | (NH4)2Fe2+5Fe3+3Al(SO4)12(H2O)18 |
| 7.CC.05 | Krausite | KFe(SO4)2 · H2O |
| 7.CC.10 | Tamarugite | NaAl(SO4)2 · 6H2O |
| 7.CC.15 | Mendozite | NaAl(SO4)2 · 11H2O |
| 7.CC.15 | Kalinite | KAl(SO4)2 · 11H2O |
| 7.CC.20 | Alum-(Na) | NaAl(SO4)2 · 12H2O |
| 7.CC.20 | Lonecreekite | (NH4)Fe3+(SO4)2 · 12H2O |
| 7.CC.20 | Alum-(K) | KAl(SO4)2 · 12H2O |
| 7.CC.20 | Tschermigite | (NH4)Al(SO4)2 · 12H2O |
| 7.CC.20 | Lanmuchangite | Tl+Al(SO4)2 · 12H2O |
| 7.CC.25 | Zincovoltaite | K2Zn5Fe3+3Al(SO4)12 · 18H2O |
| 7.CC.25 | Voltaite | K2Fe2+5Fe3+3Al(SO4)12 · 18H2O |
| 7.CC.25 | Magnesiovoltaite | K2Mg5Fe3+3Al(SO4)12 · 18H2O |
| 7.CC.25 | Pertlikite | K2(Fe2+,Mg)2(Mg,Fe3+)4Fe3+2Al(SO4)12 · 18H2O |
| 7.CC.25 | Ammoniomagnesiovoltaite | (NH4)2Mg2+5Fe3+3Al(SO4)12 · 18H2O |
| 7.CC.30 | Kröhnkite | Na2Cu(SO4)2 · 2H2O |
| 7.CC.35 | Ferrinatrite | Na3Fe(SO4)3 · 3H2O |
| 7.CC.40 | Goldichite | KFe(SO4)2 · 4H2O |
| 7.CC.45 | Löweite | Na12Mg7(SO4)13 · 15H2O |
| 7.CC.50 | Nickelblödite | Na2Ni(SO4)2 · 4H2O |
| 7.CC.50 | Blödite | Na2Mg(SO4)2 · 4H2O |
| 7.CC.50 | Changoite | Na2Zn(SO4)2 · 4H2O |
| 7.CC.55 | Leonite | K2Mg(SO4)2 · 4H2O |
| 7.CC.55 | Mereiterite | K2Fe(SO4)2 · 4H2O |
| 7.CC.60 | Nickelpicromerite | K2Ni(SO4)2 · 6H2O |
| 7.CC.60 | Nickelboussingaultite | (NH4)2Ni(SO4)2 · 6H2O |
| 7.CC.60 | Katerinopoulosite | (NH4)2Zn(SO4)2 · 6H2O |
| 7.CC.60 | Picromerite | K2Mg(SO4)2 · 6H2O |
| 7.CC.60 | Cyanochroite | K2Cu(SO4)2 · 6H2O |
| 7.CC.60 | Mohrite | (NH4)2Fe(SO4)2 · 6H2O |
| 7.CC.60 | Boussingaultite | (NH4)2Mg(SO4)2 · 6H2O |
| 7.CC.65 | Polyhalite | K2Ca2Mg(SO4)4 · 2H2O |
| 7.CC.75 | Amarillite | NaFe(SO4)2 · 6H2O |
| 7.CC.80 | Konyaite | Na2Mg(SO4)2 · 5H2O |
| 7.CC.85 | Wattevilleite | Na2Ca(SO4)2 · 4H2O (?) |
| 7.CC.85 | Xocolatlite | Ca2Mn4+2(Te6+O6)2 · H2O |
| 7.CC.90 | Eckhardite | (Ca,Pb)Cu2+Te6+O5(H2O) |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 12.1768% | 3,775 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Other Information
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 Leightonite
mindat.org URL:
https://www.mindat.org/min-2369.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Leightonite
Reference List:
Palache, Charles (1938) Leightonite, a new sulphate of copper from Chile. American Mineralogist, 23 (1) 34-37
Peacock, M. A. (1938) The relation of leightonite to polyhalite. American Mineralogist, 23 (1) 38-45
Bandy, Mark C. (1938) Mineralogy of three sulphate deposits of northern Chile. American Mineralogist, 23 (11) 669-760
Palache, Charles (1938) Leightonite, a new sulphate of copper from Chile. American Mineralogist, 23 (1) 34-37
Localities for Leightonite
Showing 13 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.
Austria | |
| |
Canada | |
| Shang (2000) |
Chile (TL) | |
| Palache (1938) +2 other references |
| Lapis 1/2008 | |
| Maurizio Dini collection (analysed by Dr. Jochen Schlüter) +1 other reference |
France | |
| Favreau et al. (2024) |
| Georges FAVREAU collection and EDX ... +1 other reference | |
Greece | |
| Rieck et al. (2018) |
Italy | |
| Balassone et al. (2019) |
| Pellino et al. (2025) | |
Namibia | |
| Gebhard (1999) |
Norway | |
| Garmo (1978) +1 other reference |
| Garmo (1978) +1 other reference |
Quick NavTopAbout LeightoniteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesCommon AssociatesStrunz-MindatRadioactivityOther InformationInternet Links References Localities Locality List
Salvadora Mine, Calama, El Loa Province, Antofagasta, Chile