Starkeyite
A valid IMA mineral species - grandfathered
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About Starkeyite
Formula:
MgSO4 · 4H2O
Colour:
White to very pale yellow or pale greenish white.
Lustre:
Dull, Earthy
Hardness:
2 - 3
Specific Gravity:
2
Crystal System:
Monoclinic
Member of:
Name:
Named in 1956 by Oliver Rudolph Grawe for the type locality, the Starkey Mine in Madison County, Missouri, USA.
Type Locality:
Rozenite Group.
Closely related to cranswickite.
This is a rare mineral, found at only a few localities, then it is usually found as white to very pale yellow or very pale greenish white powdery efflorescences. Good crystals are extremely rare, perhaps unheard of.
Closely related to cranswickite.
This is a rare mineral, found at only a few localities, then it is usually found as white to very pale yellow or very pale greenish white powdery efflorescences. Good crystals are extremely rare, perhaps unheard of.
Unique Identifiers
Mindat ID:
3752
Long-form identifier:
mindat:1:1:3752:1
Similar Names
| β-Starkeyit | A synonym of 'β-Starkeyite' |
| β-Starkeyite | A synonym of Cranswickite |
IMA Classification of Starkeyite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
MgS6+O4·4H2O
First published:
1945
Classification of Starkeyite
7.CB.15
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
B : With only medium-sized cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
B : With only medium-sized cations
Dana 7th ed.:
29.6.6.2
29.6.6.2
29 : HYDRATED ACID AND NORMAL SULFATES
6 : AXO4·xH2O
29 : HYDRATED ACID AND NORMAL SULFATES
6 : AXO4·xH2O
25.3.3
25 : Sulphates
3 : Sulphates of Mg
25 : Sulphates
3 : Sulphates of Mg
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 |
|---|---|---|
| Ske | 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 Starkeyite
Dull, Earthy
Transparency:
Translucent, Opaque
Colour:
White to very pale yellow or pale greenish white.
Streak:
White
Hardness:
2 - 3 on Mohs scale
Tenacity:
Brittle
Fracture:
Irregular/Uneven
Density:
2 g/cm3 (Measured) 2.007 g/cm3 (Calculated)
Optical Data of Starkeyite
Type:
Biaxial (+)
RI values:
nα = 1.490 nβ = 1.491 nγ = 1.497
2V:
Measured: 50° , Calculated: 46°
Birefringence:
0.007
Max. Birefringence:
δ = 0.007
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 (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.
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:
none
Pleochroism:
Non-pleochroic
Chemistry of Starkeyite
Mindat Formula:
MgSO4 · 4H2O
Element Weights:
Elements listed:
Crystallography of Starkeyite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Cell Parameters:
a = 5.92 Å, b = 13.6 Å, c = 7.91 Å
β = 90.85°
β = 90.85°
Ratio:
a:b:c = 0.435 : 1 : 0.582
Unit Cell V:
636.78 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Forms not reported, typically found as powdery efflorescences.
Twinning:
Not reported.
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) |
|---|---|---|---|---|---|---|---|
| 0009287 | Starkeyite | Baur W H (1964) On the crystal chemistry of salt hydrates. II. A neutron diffraction study of MgSO4*4H2O Acta Crystallographica 17 863-869 |  | 1964 | synthetic | 0 | 293 |
| 0009275 | Starkeyite | Baur W H (1962) Zur kristallchemie der salzhydrate. Die kristallstrukturen von MgSO4*4H2O (leonhardtit) und FeSO4*4H2O (rozenit) Acta Crystallographica 15 815-826 | | 1962 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.83 Å | (50) |
| 5.43 Å | (80) |
| 4.70 Å | (40) |
| 4.46 Å | (100) |
| 3.95 Å | (70) |
| 3.40 Å | (50) |
| 3.22 Å | (40) |
| 2.95 Å | (60) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) | |
| Stage 7: Great Oxidation Event | <2.4 |
| 45b : [Other oxidized fumarolic minerals] | |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] | |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 55 : Anthropogenic mine minerals |
Geological Setting:
A secondary mineral sometimes found in the oxidized zone of sulfide mineral deposits, resulting from the decomposition of pyrite and marcasite. May form from the dehydration of hexahydrite (Chou, 2005).
Type Occurrence of Starkeyite
General Appearance of Type Material:
Dull white powdery efflorescence.
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 105610.
Geological Setting of Type Material:
Dump material from a pyrite deposit in dolomite.
Associated Minerals at Type Locality:
Synonyms of Starkeyite
Other Language Names for Starkeyite
Varieties of Starkeyite
Relationship of Starkeyite to other Species
Member of:
Other Members of Rozenite Group:
Common Associates
Associations Based on Photo Data:
| 1 photo of Starkeyite associated with Mcallisterite | Mg2[B6O7(OH)6]2 · 9H2O |
| 1 photo of Starkeyite associated with Niahite | (NH4)Mn2+(PO4) · H2O |
| 1 photo of Starkeyite associated with Hexahydrite | Mg(H2O)6(SO4) |
| 1 photo of Starkeyite associated with Rozenite | FeSO4 · 4H2O |
| 1 photo of Starkeyite associated with Pyrite | FeS2 |
Related Minerals - Strunz-mindat Grouping
| 7.CB. | Sarvodaite | Al2(SO4)3 · 5H2O |
| 7.CB.02 | Voudourisite | CdSO4 · H2O |
| 7.CB.05 | Szmikite | MnSO4 · H2O |
| 7.CB.05 | Szomolnokite | FeSO4 · H2O |
| 7.CB.05 | Cobaltkieserite | CoSO4 · H2O |
| 7.CB.05 | Dwornikite | Ni(SO4) · H2O |
| 7.CB.05 | Kieserite | MgSO4 · H2O |
| 7.CB.05 | Poitevinite | (Cu,Fe)SO4 · H2O |
| 7.CB.05 | Gunningite | ZnSO4 · H2O |
| 7.CB.07 | Sanderite | MgSO4 · 2H2O |
| 7.CB.10 | Bonattite | CuSO4 · 3H2O |
| 7.CB.12 | Belogubite | CuZn(SO4)2 · 10H2O |
| 7.CB.15 | Drobecite | CdSO4 · 4H2O |
| 7.CB.15 | Aplowite | CoSO4 · 4H2O |
| 7.CB.15 | Cranswickite | MgSO4 · 4H2O |
| 7.CB.15 | Rozenite | FeSO4 · 4H2O |
| 7.CB.15 | Ilesite | Mn2+(SO4) · 4H2O |
| 7.CB.15 | Boyleite | ZnSO4 · 4H2O |
| 7.CB.20 | Siderotil | FeSO4 · 5H2O |
| 7.CB.20 | Jôkokuite | MnSO4 · 5H2O |
| 7.CB.20 | Pentahydrite | MgSO4 · 5H2O |
| 7.CB.20 | Chalcanthite | CuSO4 · 5H2O |
| 7.CB.25 | Chvaleticeite | Mn2+(H2O)6(SO4) |
| 7.CB.25 | Nickelhexahydrite | Ni2+(H2O)6(SO4) |
| 7.CB.25 | Hexahydrite | Mg(H2O)6(SO4) |
| 7.CB.25 | Bianchite | Zn(H2O)6(SO4) |
| 7.CB.25 | Moorhouseite | Co2+(H2O)6(SO4) |
| 7.CB.25 | Ferrohexahydrite | Fe2+(H2O)6(SO4) |
| 7.CB.30 | Retgersite | NiSO4 · 6H2O |
| 7.CB.35 | Zincmelanterite | Zn(H2O)6(SO4) · H2O |
| 7.CB.35 | Melanterite | Fe2+(H2O)6(SO4) · H2O |
| 7.CB.35 | Alpersite | (Mg,Cu2+)(H2O)6(SO4) · H2O |
| 7.CB.35 | Bieberite | Co2+(H2O)6(SO4) · H2O |
| 7.CB.35 | Boothite | Cu2+(H2O)6(SO4) · H2O |
| 7.CB.35 | Mallardite | Mn2+(H2O)6(SO4) · H2O |
| 7.CB.40 | Epsomite | MgSO4 · 7H2O |
| 7.CB.40 | Goslarite | ZnSO4 · 7H2O |
| 7.CB.40 | Morenosite | NiSO4 · 7H2O |
| 7.CB.45 | Meta-alunogen | Al2(SO4)3 · 12H2O |
| 7.CB.45 | Alunogen | Al2(SO4)3 · 17H2O |
| 7.CB.50 | Aluminocoquimbite | Al2Fe2(SO4)6(H2O)12 · 6H2O |
| 7.CB.50 | Lazaridisite | Cd3(SO4)3 · 8H2O |
| 7.CB.52 | Pararaisaite | CuMg[Te6+O4(OH)2] · 6H2O |
| 7.CB.55 | Paracoquimbite | Fe4(SO4)6(H2O)12 · 6H2O |
| 7.CB.55 | Rhomboclase | (H5O2)Fe3+(SO4)2 · 2H2O |
| 7.CB.55 | Raisaite | CuMg[Te6+O4(OH)2] · 6H2O |
| 7.CB.55 | Coquimbite | AlFe3(SO4)6(H2O)12 · 6H2O |
| 7.CB.57 | 'Caichengyunite' | Fe2+3Al2(SO4)6 · 30H2O |
| 7.CB.60 | Kornelite | Fe2(SO4)3 · 7H2O |
| 7.CB.65 | Quenstedtite | Fe2(SO4)3 · 11H2O |
| 7.CB.70 | Lausenite | Fe2(SO4)3 · 5H2O |
| 7.CB.75 | Römerite | Fe2+Fe3+2(SO4)4 · 14H2O |
| 7.CB.75 | Lishizhenite | ZnFe2(SO4)4 · 14H2O |
| 7.CB.80 | Ransomite | CuFe2(SO4)4 · 6H2O |
| 7.CB.85 | Dietrichite | ZnAl2(SO4)4 · 22H2O |
| 7.CB.85 | Halotrichite | Fe2+Al2(SO4)4 · 22H2O |
| 7.CB.85 | Apjohnite | Mn2+Al2(SO4)4 · 22H2O |
| 7.CB.85 | Redingtonite | Fe2+Cr3+2(SO4)4 · 22H2O |
| 7.CB.85 | Pickeringite | MgAl2(SO4)4 · 22H2O |
| 7.CB.85 | Bílinite | Fe2+Fe3+2(SO4)4 · 22H2O |
| 7.CB.85 | Wupatkiite | Co2+Al2(SO4)4 · 22H2O |
| 7.CB.90 | Meridianiite | MgSO4 · 11H2O |
Other Information
Notes:
Soluble in H2O.
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 Starkeyite
mindat.org URL:
https://www.mindat.org/min-3752.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 Starkeyite
Reference List:
Robson, Homer Louis (1927) The system MgSO4·H2O from 68 to 240°. Journal Of The American Chemical Society, 49 (11). 2772-2783 doi:10.1021/ja01410a016
Baur, W. H. (1962) Zur Kristallchemie der Salzhydrate. Die Kristallstrukturen von MgSO4.4H2O (Leonhardtit) und FeSO4.4H2O (Rozenit). Acta Crystallographica, 15 (9). 815-826 doi:10.1107/s0365110x62002200
Baur, W. H. (1964) On the crystal chemistry of salt hydrates. II. A neutron diffraction study of MgSO4.4H2O. Acta Crystallographica, 17 (7) 863-869 doi:10.1107/s0365110x64002304
Localities for Starkeyite
Showing 105 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.
Antarctica | |
| Li et al. (2003) |
Argentina | |
| Peterson (2011) |
Australia | |
| Wilson et al. (2014) |
Austria | |
| Exel (1993) |
Canada | |
| Sabina (1972) |
| Sabina (2003) +1 other reference |
| Shang (2000) |
Chile | |
| Anthony (1997) |
| Marta et al. (1996) |
| Pueyo et al. (2021) +1 other reference |
China | |
| Shaoxiu (1991) |
| Tang (2005) |
Costa Rica | |
| Ulloa et al. (2018) |
Czech Republic | |
| Matýsek et al. (2014) |
| Matýsek et al. (2014) |
| Matýsek et al. (2026) | |
| Hršelová et al. (2013) |
Greece | |
| Blaß et al. (1998) |
| Wendel et al. (1999) | |
| Skarpelis et al. (2004) |
Hungary | |
| |
| Szakáll: Minerals of Rudabánya +1 other reference |
| Szakáll: Minerals of Rudabánya +1 other reference | |
| Szakáll: Minerals of Rudabánya +1 other reference | |
| Sándor et al. (2005) |
| Szakáll et al. (1997) |
| |
Iceland | |
| Carson III (2015) |
India | |
| Sinha et al. (2003) |
Italy | |
| Del Caldo et al. (1973) |
| C.L. Garavelli (1957) |
Japan | |
| Seki et al. (1987) |
| - (n.d.) |
Lebanon | |
| Kruszewski (2019) |
Mexico | |
| Gazquez et al. (1) |
| Yta et al. (2005) |
Morocco | |
| Hakkou et al. (2008) |
Namibia | |
| Dill et al. (2002) |
North Macedonia | |
| Rieck (1993) +1 other reference |
| Boev et al. (2015) | |
Pakistan | |
| M. Qasim Jan et al. (1985) |
Peru | |
| Smuda +4 other references |
Poland | |
| Cabała et al. (2008) |
| Ciesielczukk |
| Parafiniuk et al. (2009) |
| Kruszewski et al. (2020) |
Portugal | |
| Oliveira et al. (2024) |
Romania | |
| A. Januszewska PXRD data / Januszewska et al. (in preparation) |
Russia | |
| Cesnokov et al. (1998) |
| Okrugin (2004) |
| N.V. et al. (2019) |
| Kasatkin et al. (2021) |
| Kasatkin et al. (2014) |
Senegal | |
| Montoroi (1995) |
Slovakia | |
| Koděra et al. (1986) |
| Ďuďa |
| Koděra et al. (1986) |
| Ďuďa R. et al. (1985) |
Spain | |
| Valente et al. (2013) |
| Romero et al. (2006) +1 other reference |
| Buey et al. (2025) |
| Buey et al. (2025) | |
| Buey et al. (2025) | |
| FMF Forum |
Sweden | |
| The Sulfur Problem. Proceedings 8th ... +1 other reference |
Switzerland | |
| Romani (2000) |
| Romani (2000) | |
| Romani (2000) | |
| Romani (2000) +1 other reference |
| Analyses Nicolas Meisser (15/11/2017) |
Tunisia | |
| Smykatz-Kloss et al. (2010) |
Turkey | |
| Helvaci (1998) |
| van Doesburg et al. (1982) |
UK | |
| Smith et al. (2014) |
Ukraine | |
| Dobrovolskaya T.I. (2004) |
USA | |
| Wenrich (1988) +1 other reference |
| Anthony et al. (1976) +1 other reference |
| Dunning et al. (2002) |
| [var: Iron-bearing Starkeyite] Snetsinger (1973) +3 other references |
| California Geology: 48 (5) | |
| Adams et al. (2014) |
| Adams et al. (2014) |
| Eckel et al. (1997) |
| Eckel et al. (1997) |
| Eckel et al. (1997) |
| Eckel et al. (1997) |
| Eckel et al. (1997) |
| Eckel et al. (1997) |
| Milton (1977) | |
| Heinrich et al. (2004) |
| Am Min 41:662 +3 other references |
| Barrick Gold Corporation |
| Dunn (1995) |
| Flohr et al. (1995) |
| Rocks & Min. | |
| Dietrich (1990) |
| Dietrich (1990) | |
| Dietrich (1990) | |
| Dietrich (1985) |
| Dietrich (1990) | |
| Dietrich (1990) |
| Kilburn et al. (1996) |
Zimbabwe | |
| Frei (2005) |
Mars | |
| Chipera et al. (2023) |
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Mosnico-Sanico road, Vendrogno, Lecco Province, Lombardy, Italy