Marécottite
A valid IMA mineral species
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About Marécottite
Entrance to the exploration gallery
La Creusaz U prospect, La Creusaz, Les Marécottes, Salvan, Saint-Maurice, Valais, Switzerland
La Creusaz U prospect, La Creusaz, Les Marécottes, Salvan, Saint-Maurice, Valais, Switzerland
Formula:
Mg3(UO2)8(SO4)4O6(OH)2 · 28H2O
Colour:
Yellow-orange
Lustre:
Vitreous
Hardness:
3
Specific Gravity:
4.03
Crystal System:
Triclinic
Name:
For the village of Les Marécottes, whose church is 1100 meters from the type locality.
Related to the minerals of the zippeite group and closely related to hubbardite.
See especially also magnesiozippeite.
See especially also magnesiozippeite.
Name Encoding
ASCII-7:
Marecottite
Unique Identifiers
Mindat ID:
27152
Long-form identifier:
mindat:1:1:27152:5
Classification of Marécottite
The zippeite-type sheet
The zippeite-like uranyl sulfate sheet topology found in marécottite.
IMA Classification of Marécottite
Approved
IMA Formula:
Mg(H2O)6]3[(U6+O2)4O3(OH)(S6+O4)2]2·8H2O
Approval year:
2001
First published:
2003
7.EC.15
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
E : Uranyl sulfates
C : With medium-sized and large cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
E : Uranyl sulfates
C : With medium-sized and large cations
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 |
|---|---|---|
| Mco | 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 Marécottite
Vitreous
Transparency:
Transparent
Colour:
Yellow-orange
Streak:
White ("colorless")
Hardness:
3 on Mohs scale
Tenacity:
Very brittle
Cleavage:
Perfect
(011)
(011)
Density:
4.03 g/cm3 (Measured) 3.83 g/cm3 (Calculated)
Optical Data of Marécottite
Type:
Biaxial
RI values:
n = 1.735 - 1.75
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
Pleochroism:
Visible
Comments:
Pale yellow to orange yellow
Chemistry of Marécottite
Mindat Formula:
Mg3(UO2)8(SO4)4O6(OH)2 · 28H2O
Element Weights:
Crystallography of Marécottite
Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 10.815 Å, b = 11.249 Å, c = 13.852 Å
α = 66.224°, β = 72.412°, γ = 69.995°
α = 66.224°, β = 72.412°, γ = 69.995°
Ratio:
a:b:c = 0.961 : 1 : 1.231
Unit Cell V:
1422.1 ų
Twinning:
Common, perpendicular to (011)
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.46 Å | (100) |
| 4.73 Å | (80) |
| 3.44 Å | (80) |
| 3.39 Å | (70) |
| 2.88 Å | (30) |
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] | |
| 47f : [Uranyl (U⁶⁺) minerals] | |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 55 : Anthropogenic mine minerals |
Geological Setting:
Weathered uranium deposits
Type Occurrence of Marécottite
General Appearance of Type Material:
Diamond shaped platelets to 500 µm, commonly twinned, and grouped into rosettes.
Place of Conservation of Type Material:
Musée Géologique Cantonal at Lausanne, Switzerland. Holotype MGL58285 and cotype MGL58290.
Geological Setting of Type Material:
Recently formed alteration products of uraninite. Stockpiled uranium ore and associated sulfides, in an underground mine, subjected to acid mine drainage water, atmospheric oxygen, and bacterial activity.
Associated Minerals at Type Locality:
Synonyms of Marécottite
Other Language Names for Marécottite
Relationship of Marécottite to other Species
Structurally related to group(s):
| Zippeite Group | A group of metal uranyl sulphates with layered structures. |
Common Associates
Associations Based on Photo Data:
| 19 photos of Marécottite associated with Natrozippeite | Na5(UO2)8(SO4)4O5(OH)3 · 12H2O |
| 13 photos of Marécottite associated with Gypsum | CaSO4 · 2H2O |
| 6 photos of Marécottite associated with Nickelzippeite | Ni2(UO2)6(SO4)3(OH)10 · 16H2O |
| 5 photos of Marécottite associated with Uraninite | UO2 |
| 3 photos of Marécottite associated with Magnesiozippeite | Mg(UO2)2(SO4)O2 · 3.5H2O |
| 2 photos of Marécottite associated with Zippeite Group | |
| 2 photos of Marécottite associated with 'Sandstone' | |
| 2 photos of Marécottite associated with Devilline | CaCu4(SO4)2(OH)6 · 3H2O |
| 1 photo of Marécottite associated with Bayleyite | Mg2(UO2)(CO3)3 · 18H2O |
| 1 photo of Marécottite associated with Thérèsemagnanite | NaCo4(SO4)(OH)6Cl · 6H2O |
Related Minerals - Strunz-mindat Grouping
| 7.EC. | Nitscheite | (NH4)2[(UO2)2(SO4)3(H2O)2] · 3H2O |
| 7.EC. | Beshtauite | (NH4)2(UO2)(SO4)2 · 2H2O |
| 7.EC. | Oldsite-(K) | K2Fe2+[(UO2)(SO4)2]2(H2O)8 |
| 7.EC. | Adolfpateraite | K(UO2)(SO4)(OH)(H2O) |
| 7.EC. | Libbyite | (NH4)2(Na2◻)[(UO2)2(SO4)3(H2O)]2 · 7H2O |
| 7.EC. | Seaborgite | LiK2Na6(UO2)(SO4)5(SO3OH)(H2O) |
| 7.EC.05 | Zinczippeite | Zn(UO2)2(SO4)O2 · 3.5H2O |
| 7.EC.05 | Zippeite | K3(UO2)4(SO4)2O3(OH) · 3H2O |
| 7.EC.05 | Cobaltzippeite | Co(UO2)2(SO4)O2 · 3.5H2O |
| 7.EC.05 | Nickelzippeite | Ni2(UO2)6(SO4)3(OH)10 · 16H2O |
| 7.EC.05 | Redcanyonite | (NH4)2Mn[(UO2)4O4(SO4)2](H2O)4 |
| 7.EC.05 | Natrozippeite | Na5(UO2)8(SO4)4O5(OH)3 · 12H2O |
| 7.EC.05 | Magnesiozippeite | Mg(UO2)2(SO4)O2 · 3.5H2O |
| 7.EC.05 | Ammoniozippeite | (NH4)2[(UO2)2(SO4)O2] · H2O |
| 7.EC.05 | Plavnoite | K0.8Mn0.6[(UO2)2O2(SO4)] · 3.5H2O |
| 7.EC.10 | Rabejacite | Ca(UO2)4(SO4)2(OH)6 · 6H2O |
| 7.EC.10 | Svornostite-(NH4) | (NH4)2Mg(UO2)2(SO4)4(H2O)8 |
| 7.EC.10 | Svornostite-(K) | K2Mg[(UO2)(SO4)2]2(H2O)8 |
| 7.EC.15 | Sejkoraite-(Y) | Y2(UO2)8(SO4)4O6(OH)2 · 26H2O |
| 7.EC.15 | Hubbardite | Mg(H2O)6[(UO2)2O(OH)(SO4)]2 · 8H2O |
| 7.EC.20 | Pseudojohannite | Cu3(UO2)4(SO4)2O4(OH)2 · 12H2O |
| 7.EC.40 | Bluelizardite | Na7(UO2)(SO4)4Cl(H2O)2 |
| 7.EC.45 | Meisserite | Na5(UO2)(SO4)3(SO3OH)(H2O) |
| 7.EC.45 | Fermiite | Na4(UO2)(SO4)3 · 3H2O |
| 7.EC.45 | Oppenheimerite | Na2(UO2)(SO4)2 · 3H2O |
| 7.EC.50 | Feynmanite | Na(UO2)(SO4)(OH) · 3.5H2O |
| 7.EC.50 | Plášilite | Na(UO2)(SO4)(OH) · 2H2O |
| 7.EC.55 | Geschieberite | K2(UO2)(SO4)2 · 2H2O |
| 7.EC.60 | Ottohahnite | Na6(UO2)2(SO4)5(H2O)7 · 1.5H2O |
| 7.EC.65 | Péligotite | Na6(UO2)(SO4)4 · 4H2O |
| 7.EC.70 | Klaprothite | Na6(UO2)(SO4)4 · 4H2O |
| 7.EC.75 | Lussierite | Na10[(UO2)(SO4)4](SO4)2 · 3(H2O) |
| 7.EC.80 | Navrotskyite | K2Na10(UO2)3(SO4)9 · 2H2O |
| 7.EC.85 | Pseudomeisserite-(NH4) | (NH4)2Na4[(UO2)2(SO4)5] · 4H2O |
| 7.EC.90 | Wetherillite | Na2Mg(UO2)2(SO4)4 · 18H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 58.5588% | 14,639,700 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 0.0000% | 0 | 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 Marécottite
Not fluorescent
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 Marécottite
mindat.org URL:
https://www.mindat.org/min-27152.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Marécottite
Reference List:
Brugger, J., Burns, Peter C., Meisser, N. (2003) Contribution to the mineralogy of acid drainage of Uranium minerals: Marecottite and the zippeite-group. American Mineralogist, 88 (4) 676-685 doi:10.2138/am-2003-0421
Localities for Marécottite
Showing 14 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.
Czech Republic | |
| Am Min 88:4 pp 676-685 |
| Tvrdý et al. (2010) | |
| Plášil et al. (2014) | |
| Tvrdý et al. (2010) |
| Thorne (n.d.) +1 other reference |
| Petr Pauliš |
Germany | |
| Möhn et al. (07/2020) |
| Witzke (2024) |
Italy | |
| Campostrini I. (2013) |
Switzerland (TL) | |
| Brugger et al. (2003) +1 other reference |
USA | |
| Brugger et al. (2003) |
| Collected by and in the collection of ... |
| Collected by Joe Marty +1 other reference | |
| Collected by Pat Haynes and analysis ... |
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Markey Mine, Red Canyon Mining District, San Juan County, Utah, USA