Krausite
A valid IMA mineral species - grandfathered
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About Krausite
Edward Henry Kraus
Formula:
KFe(SO4)2 · H2O
Colour:
Pale lemon yellow, yellowish green, gray; colourless to pale yellow in transmitted light.
Lustre:
Sub-Vitreous, Waxy, Earthy
Hardness:
2½
Specific Gravity:
2.84
Crystal System:
Monoclinic
Name:
Named by William F. Foshag in honor of Dr. Edward Henry Kraus [December 1, 1875 Syracuse, New York, USA - February 3, 1973 Ann Arbor, Michigan, USA], American mineralogist, University of Michigan.
This page provides mineralogical data about Krausite.
Unique Identifiers
Mindat ID:
2270
Long-form identifier:
mindat:1:1:2270:1
Similar Names
| Crossite | A discredited species name | |
| Crucite (of Delamétherie) | A synonym of 'Chiastolite' | |
| Crucite (of Thomson) | A synonym of 'Crucilite' | |
| Grossite | A valid IMA mineral species | CaAl4O7 |
| Kerusit | A synonym of Cerussite | |
| Kraurite | A synonym of Dufrénite | |
| Krautite | A valid IMA mineral species | Mn(HAsO4) · H2O |
| Kryzaite | A valid IMA mineral species - pending publication | Na4(MgCr)(PO4)3 |
| Kyrosite | A synonym of 'Lonchidite' |
IMA Classification of Krausite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
KFe3+(S6+O4)2·H2O
Classification of Krausite
7.CC.05
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
29.5.1.1
29 : HYDRATED ACID AND NORMAL SULFATES
5 : AB(XO4)2·xH2O
29 : HYDRATED ACID AND NORMAL SULFATES
5 : AB(XO4)2·xH2O
25.11.7
25 : Sulphates
11 : Sulphates of Fe and other metals
25 : Sulphates
11 : Sulphates of Fe and other metals
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 |
|---|---|---|
| Ksi | 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 Krausite
Sub-Vitreous, Waxy, Earthy
Transparency:
Transparent, Translucent
Comment:
Not vitreous
Colour:
Pale lemon yellow, yellowish green, gray; colourless to pale yellow in transmitted light.
Streak:
White
Hardness:
2½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
Perfect on {001}; Good on {100}
Perfect on {001}; Good on {100}
Density:
2.84 g/cm3 (Measured) 2.839 g/cm3 (Calculated)
Optical Data of Krausite
Type:
Biaxial (+)
RI values:
nα = 1.588 nβ = 1.65 nγ = 1.722
2V:
Measured: 75°
Birefringence:
0.034
Max. Birefringence:
δ = 0.134
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 (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:
relatively strong
Optical Extinction:
Z=b, Y^c = -35°
Pleochroism:
Visible
Comments:
X = Colourless
Y = Pale yellow
Z = Pale yellow
Y = Pale yellow
Z = Pale yellow
Comments:
2V large
Chemistry of Krausite
Mindat Formula:
KFe(SO4)2 · H2O
Element Weights:
Crystallography of Krausite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/m
Setting:
P21/m
Cell Parameters:
a = 7.91 Å, b = 5.15 Å, c = 8.99 Å
β = 102.75°
β = 102.75°
Ratio:
a:b:c = 1.536 : 1 : 1.746
Unit Cell V:
357.19 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Commonly earthy to finely granular. Crystals may be short prismatic [001]; also equant to tabular {001}. Larger crystals tend to be rough and opaque, smaller ones brilliant and clear.
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) |
|---|---|---|---|---|---|---|---|
| 0001008 | Krausite | Effenberger H, Pertlik F, Zemann J (1986) Refinement of the crystal structure of krausite: a mineral with an interpolyhedral oxygen-oxygen contact shorter than the hydrogen bond American Mineralogist 71 202-205 |  | 1986 | 0 | 293 | |
| 0000141 | Krausite | Graeber E J, Morosin B, Rosenzweig A (1965) The crystal structure of krausite, KFe(SO4)2.H2O American Mineralogist 50 1929-1936 | | 1965 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.69 Å | (70) |
| 4.40 Å | (80) |
| 4.26 Å | (50) |
| 3.69 Å | (70) |
| 3.09 Å | (100) |
| 2.77 Å | (40) |
| 2.58 Å | (40) |
| 2.55 Å | (40) |
Comments:
ICDD 18-1028
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 45a : [Sulfates, arsenates, selenates, antimonates] | |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] | |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 55 : Anthropogenic mine minerals |
Geological Setting:
Oxidation material on pyrite bearing dumps.
Type Occurrence of Krausite
Place of Conservation of Type Material:
Smithsonian Institution, Washington DC
Geological Setting of Type Material:
Secondary mineral in sulfate bearing chert.
Associated Minerals at Type Locality:
Other Language Names for Krausite
Common Associates
Associations Based on Photo Data:
| 41 photos of Krausite associated with Römerite | Fe2+Fe3+2(SO4)4 · 14H2O |
| 27 photos of Krausite associated with Coquimbite | AlFe3(SO4)6(H2O)12 · 6H2O |
| 25 photos of Krausite associated with Halotrichite | Fe2+Al2(SO4)4 · 22H2O |
| 7 photos of Krausite associated with Metavoltine | K2Na6Fe2+Fe3+6O2(SO4)12 · 18H2O |
| 5 photos of Krausite associated with Voltaite | K2Fe2+5Fe3+3Al(SO4)12 · 18H2O |
| 5 photos of Krausite associated with Goldichite | KFe(SO4)2 · 4H2O |
| 4 photos of Krausite associated with Magnesiocopiapite | MgFe3+4(SO4)6(OH)2 · 20H2O |
| 4 photos of Krausite associated with Native Sulphur | S8 |
| 3 photos of Krausite associated with 'Copper-bearing Melanterite' | (Fe,Cu)SO4 · 7H2O |
| 2 photos of Krausite associated with Copiapite | Fe2+Fe3+4(SO4)6(OH)2 · 20H2O |
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.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.70 | Leightonite | K2Ca2Cu(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) | 12.8156% | 3,973 | 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
Fluorescence of Krausite
Not fluorescent
Other Information
Notes:
Slowly decomposed by water leaving ferric oxide.
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 Krausite
mindat.org URL:
https://www.mindat.org/min-2270.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Krausite
Reference List:
Foshag, William F. (1931) Krausite, a new sulfate from California. American Mineralogist, 16 (9) 352-360
Graeber, Edward J., Rosenzweig, Abraham (1965) The unit cell of krausite. American Mineralogist, 50 (3-4) 504-507
Localities for Krausite
Showing 32 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.
Argentina | |
| rruff.geo.arizona.edu (n.d.) +2 other references |
Canada | |
| Shang (2000) |
Chile | |
| Samples analysed by Dr. Jochen Schluter +5 other references |
| Natural History Museum Vienna collection (Uwe Kolitsch SXRD on Arturo Molina material) |
China | |
| Xu Ying-xia et al. (2006) |
France | |
| Gol et al. (2010) |
| Gol et al. (2010) | |
| Georges FAVREAU collection & EDX ... |
Germany | |
| Thalheim +1 other reference |
Greece | |
| Rieck (n.d.) |
| Dr. A. Godelitsas collection and ... +1 other reference |
| Rieck (n.d.) | |
| Rieck (n.d.) |
| Markus J. Stark Collection |
Hungary | |
| collector: Gábor Koller +1 other reference |
Italy | |
| rruff.geo.arizona.edu (n.d.) |
| Russo et al. (2017) |
| Russo et al. (2017) | |
| De Michele (1974) +1 other reference | |
| Campostrini et al. (2010) |
| Mauro (2020) |
| Mauro D. (2016) | |
| Biagioni et al. (2019) +1 other reference |
Mexico | |
| Foshag (1931) +2 other references |
Peru | |
| Hyršl (2010) +2 other references |
Poland | |
| Cu +2 other references |
Romania | |
| Ł. Kruszewski & M. Cegiełka PXRD data +1 other reference |
Spain | |
| Calvo Rebollar et al. (2022) |
USA | |
| Palache et al. (1951) |
| part 2 +7 other references |
| Thorne (n.d.) |
| rruff.geo.arizona.edu (n.d.) |
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Willi Agatz mine, Dresden, Saxony, Germany