Melcherite (original) (raw)

A valid IMA mineral species

About MelcheriteHide

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Formula:

Ba2Na2Mg[Nb6O19] · 6H2O

Originally approved as BaCa2MgNb6O19·6H2O, but formula was revised very soon after approval.

Specific Gravity:

3.733 (Calculated)

Name:

Named in honor of Geraldo Conrado Melcher (1924-2011), professor and head of the Department of Mining and Petroleum Engineering of the Polytechnic School of the University of São Paulo, Brazil, for his pioneering studies on Jacupiranga carbonatites.

A hexaniobate related to peterandresenite.

Melcherite has structural layers parallel to the xy plane that stack along the _c_-axis with simultaneous 1/3 [1 -1 0] displacement so as to produce a R lattice. The melcherite structure is built by layers of [(Ba,K)(O,H2O)9] polyhedra and the [Nb6O19]8− super-octahedron (Lindqvist anion) interconnected by [(Na,Ca)O6] polyhedra. Mg2+ cations are bonded to six water molecules each and are not associated with Lindqvist oxygen ions (Andrade et al. 2018]

Unique IdentifiersHide

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Long-form identifier:

mindat:1:1:46639:0

7953e63b-aabe-4113-b421-5c57a504427a

IMA Classification of MelcheriteHide

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Approval history:

Soon after the approval of the new mineral melcherite (IMA No. 2015-018; see CNMNC Newsletter 25), the authors of the proposal have communicated results of subsequent analytical work on this mineral, which verifies essential contents of sodium. The new data were examined carefully by the CNMNC officers and were found reliable. The revised simplified formula, Ba2Na2Mg[Nb6O19]·6H2O, has been approved.

Type description reference:

Andrade, Marcelo B., Atencio, Daniel, Menezes Filho, Luiz A. D., Spratt, John (2018) Melcherite, trigonal Ba2Na2Mg[Nb6O19]·6H2O, the second natural hexaniobate, from Cajati, São Paulo, Brazil: Description and crystal structure. Mineralogical Magazine, 82 (1) 111-120 doi:10.1180/minmag.2017.081.026

Classification of MelcheriteHide

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7.GB.60

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
G : Molybdates, Wolframates and Niobates
B : With additional anions and/or H2O

Mineral SymbolsHide

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As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Physical Properties of MelcheriteHide

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Density:

3.733 g/cm3 (Calculated)

Chemistry of MelcheriteHide

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Mindat Formula:

Ba2Na2Mg[Nb6O19] · 6H2O

Originally approved as BaCa2MgNb6O19·6H2O, but formula was revised very soon after approval.

Chemical AnalysisHide

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Empirical formulas:

Sample references:

Crystallography of MelcheriteHide

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Class (H-M):

3 - Rhombohedral

Cell Parameters:

a = 9.0117(6) Å, c = 23.399(2) Å

Morphology:

Irregular, tabular crystals up to 200 μm in maximum dimension.

Comment:

Chemical composition varies from Ba2Na2Mg[Nb6O19].6H2O to (BaK)(NaCa)Mg[Nb6O19].6H2O. Crystal data from the second composition

X-Ray Powder DiffractionHide

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Powder Diffraction Data:

Comments:

From Type Description.

Geological EnvironmentHide

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Type Occurrence of MelcheriteHide

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General Appearance of Type Material:

As irregular, tabular crystals up to 200 μm in a vug in the carbonatite

Place of Conservation of Type Material:

Type material is deposited in the collections of the Museu de Geociências, Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080 - São Paulo, SP, Brazil, specimen number DR982

Empirical Formula of Type Material:

(Ba0.99K1.00)Σ 1.99(Na1.02Ca0.96)Σ1.98(Mg0.95Mn0.05)Σ1.00Nb6.02O19.00·6H2O

Geological Setting of Type Material:

Associated Minerals at Type Locality:

Reference:

Andrade, M.B., Atencio, D., Menezes Filho, L.A.D., Spratt, J. (2018) Melcherite, trigonal Ba2Na2Mg[Nb6O19].6H2O, the second natural hexaniobate, from Cajati, São Paulo, Brazil: Description and crystal structure. Mineralogical Magazine: 82: 111-120.

Synonyms of MelcheriteHide

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Related Minerals - Strunz-mindat GroupingHide

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Fluorescence of MelcheriteHide

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Other InformationHide

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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 MelcheriteHide

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References for MelcheriteHide

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Reference List:

Andrade, Marcelo B., Atencio, Daniel, Menezes Filho, Luiz A. D., Spratt, John (2018) Melcherite, trigonal Ba2Na2Mg[Nb6O19]·6H2O, the second natural hexaniobate, from Cajati, São Paulo, Brazil: Description and crystal structure. Mineralogical Magazine, 82 (1) 111-120 doi:10.1180/minmag.2017.081.026

Localities for MelcheriteHide

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This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

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- 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.