Chvaleticeite is a
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic ...
hexahydrite
manganese
Manganese is a chemical element with the Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of ...
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...
sulfate mineral
The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal veins and as secondary mine ...
with formula: (Mn
2+, Mg)
4">O4�6(H
2O). It occurs in the oxidized zone of manganese silicate deposits with
pyrite
The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic Luster (mineralogy), lust ...
and
rhodochrosite
Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its (rare) pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. It streaks white, and its Mohs hardness varies bet ...
that have undergone regional and
contact metamorphism
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of che ...
. It is defined as the manganese dominant member of the
hexahydrite group.
Chvaleticeite is named after the city
Chvaletice
Chvaletice () is a town in Pardubice District in the Pardubice Region of the Czech Republic. It has about 2,900 inhabitants.
Administrative parts
The village of Hornická Čtvrť is an administrative part of Chvaletice.
Geography
Chvaletice is l ...
,
Bohemia
Bohemia ( ; cs, Čechy ; ; hsb, Čěska; szl, Czechy) is the westernmost and largest historical region of the Czech Republic. Bohemia can also refer to a wider area consisting of the historical Lands of the Bohemian Crown ruled by the Bohem ...
, in the
Czech Republic
The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...
. Chvaleticeite and minerals like it have been studied for their
hydrogen bonding
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a l ...
and
incongruent melting
Incongruent melting occurs when a solid substance does not melt uniformly, so that the chemical composition of the resulting liquid is not the same as that of the original solid. During incongruent melting a new solid of different composition form ...
properties as they are predicted to form in the relative environments of Mars and other bodies in the solar system.
Structure
The structure in chvaleticeite is made by
hydrogen bonding
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a l ...
in metallic sulfates. Due to the minute grain size of chvaleticeite, typical single crystal methods could not be used. Through analogy with hexahydrite the Guinier powder diffraction method was used to identify the following structural parameters:
space group
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...
C 2/c, a = 10.05(2) Å, b = 7.24(2) Å, c = 24.3(1) Å; β = 98.0(2)°, V = 1754 Å
3, Z = 8, Dx = 1.84 g·cm
−3; a : b : c = 1.3881 : 1 : 3.3564.
Composition
Chvaleticeite has an empirical formula of (Mn
2+, Mg)
4">O4�6(H
2O) and is a member of the hexahydrite group with the space group C2/c. Chemical analysis was carried out using classical chemical methods. Sulfate was determined gravimetrically, MnO was determined using titration, MgO was determined by EDTA titration and CaO, Fe
2O
3, K
2O and Na
2O using AAS. The H
2O was determined by the modified Penfield method. The performed analysis produced the following result: MnO 15.81, MgO 6.41, CaO 0.04, FeO traces, Fe
2O
3 0.10, Al
2O
3 traces, K
2O 0.005, Na
2O 0.011, SO
3 31.48, P
2O
5 traces, H
2O+ 0.37, H
2O- 45.22, insoluble residue 0.36, sum 99.81 weight percent.
Occurrence
Chvaleticeite was discovered in a sulfate
paragenesis Paragenesis is a petrologic concept meaning an ''equilibrium sequence of mineral phases''. It is used in studies of igneous and metamorphic rock genesis and importantly in studies of the hydrothermal deposition of ore minerals and the rock altera ...
in the
oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...
zone of the Upper
Proterozoic
The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided i ...
volcanogenic massive sulfide ore deposit
Volcanogenic massive sulfide ore deposits, also known as VMS ore deposits, are a type of metal sulfide ore deposit, mainly copper-zinc which are associated with and created by volcanic-associated hydrothermal events in submarine environments.
...
of pyrite-manganese ores at Chvaletice. It was found in association with
melanterite
Melanterite is a mineral form of hydrous iron(II) sulfate: FeSO4·7H2O. It is the iron analogue of the copper sulfate chalcanthite. It alters to siderotil by loss of water. It is a secondary sulfate mineral which forms from the oxidation of prim ...
(it can form by partial dehydration), Mg-
jokouite, Mg-
ilesite,
rozenite
Rozenite is a hydrous iron sulfate mineral, Fe2+SO4•4(H2O).
It occurs as a secondary mineral, formed under low humidity at less than as an alteration of copper-free melanterite, which is a post mine alteration product of pyrite or marcasite. It ...
,
copiapite
Copiapite is a hydrated iron sulfate mineral with formula: Fe2+Fe3+4(SO4)6(OH)2·20(H2O). Copiapite can also refer to a mineral group, the copiapite group.
Copiapite is strictly a secondary mineral forming from the weathering or oxidation of iro ...
and
gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
. This paragenesis allows heptahydrates and tetrahydrates to dominate over pentahydrates and hexahydrates. Chvaleticeite is completely soluble in water.
References
{{Reflist
* Bauer, W.H. (1962) Zur Krisallchemie der Salzhydrate. Die Kristallstrukturen von (Mn, Mg)SO4x6H2O(Leonhardit) und FeSO4x4H2O(Rozenit). Acta Crystallogr., 15, 815-826.
* Bernard, J.H. et al. (1981) Petrology and geochemistry of the Upper Proterozoic Fe-Mn deposits Chvaletice, Mineralogie Ceskoslovenska – 2nd ed., Academia, Praha. Chab, J. et al. (1986)(Bohemia, Czechoslovakia). – Sbor. Geol. Ved, Lozisk. Geol. Miner., 23 118 69, Praha.
* Blake, A., Cooke, P., Hubberstey, P., and Sampson, C. (2001) Zinc(II) sulphate tetrahydrate. Acta Crystallographica E, 57, i109–i111.
* Jennifer L. Anderson et al. (2012) The atomic structure of deuterated boyleite ZnSO4·4D2O, ilesite MnSO4·4D2O, and bianchite ZnSO4·6D2O, American Mineralogist Volume 97, 1905–1914.
* Kellersohn, T. (1992) Structure of Cobalt Sulfate Tetrahydrate. Acta Crystallogr. C48, 776±779.
* Palache, C., H. Berman, and C. Frondel (1951) Dana’s system of mineralogy, (7th edition), II, 486-487.
*Petr Ondrus, Frantiesk Veselovsky, Jan Hlousek. Et al (1997) Secondary minerals of the Jachymov (Joachimsthal) ore district: Journal of the Czech Geological Society., 12 16 17 18.
* R.C. Peterson et al. (2007) Meridianiite: A new mineral species observed on Earth and predicted to exist on Mars, American Mineralogist Volume 92, 1756-1759.
Sulfate minerals
Monoclinic minerals
Minerals in space group 15