Medaite (original) (raw)

A valid IMA mineral species

About MedaiteHide

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Formula:

Mn2+6V5+Si5O18(OH)

Mn may be replaced by minor Ca, and V by minor As.

Specific Gravity:

3.65 - 3.75

Crystal System:

Monoclinic

Name:

Named in 1981 by Carlo M. Gramaccioli, William L. Giffin, and Annibale Mottana in honor of Dr. Francesco Meda (20 September 1926, Turin - 13 September 1977, Turin), an amateur mineralogist whose 'enthusiastic activity as a teacher has contributed to making mineralogy popular in Italy'.

Unique IdentifiersHide

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Long-form identifier:

mindat:1:1:2624:2

7f270cdb-8915-4b04-8709-bf30fe5a9208

IMA Classification of MedaiteHide

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Type description reference:

Classification of MedaiteHide

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9.BJ.30

9 : SILICATES (Germanates)
B : Sorosilicates
J : Sorosilicates with Si3O10, Si4O11, etc. anions; cations in octahedral [6] and greater coordination

57.4.1.1

57 : SOROSILICATES Si3O10 Groups and Larger Noncyclic Groups
4 : Insular Si3O10 and Larger Noncyclic Groups with groups with 6 or more tetrahedra

17.7.5

17 : Silicates Containing other Anions
7 : Silicates with vanadate, arsenate or antimonate

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.

Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.

Physical Properties of MedaiteHide

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Cleavage:

Distinct/Good
{100} good

Parting:

Distinct normal to elongation

Density:

3.65 - 3.75 g/cm3 (Measured) 3.727 g/cm3 (Calculated)

Optical Data of MedaiteHide

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RI values:

_n_α = 1.770(2) _n_β = 1.780(1) _n_γ = 1.800(2)

2V:

Measured: 71° , Calculated: 72°

δ = 0.030

Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.

Dispersion:

r > v distinct

Comments:

Dark to lighter orange

Comments:

X = a; Y = b; Z = c; X Λ ⊥ to cleavage = 3°.

Chemistry of MedaiteHide

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Mindat Formula:

Mn2+6V5+Si5O18(OH)

Mn may be replaced by minor Ca, and V by minor As.

Crystallography of MedaiteHide

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Crystal System:

Monoclinic

Class (H-M):

2/m - Prismatic

Cell Parameters:

a = 6.712(1) Å, b = 28.948(8) Å, c = 7.578(2) Å
β = 95.4(2)°

Ratio:

a:b:c = 0.232 : 1 : 0.262

Unit Cell V:

1,465.86 ų (Calculated from Unit Cell)

Twinning:

Microscopic symmetrical twinning. The twin plane is coincident with {100}.

Comment:

Space Group: P21/n:

Crystal StructureHide

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ID	Species	Reference	Link	Year	Locality	Pressure (GPa)	Temp (K)
0009748	Medaite	Gramaccioli C M, Liborio G, Pilati T (1981) Structure of medaite, Mn6[VSi5O18(OH)]: The presence of a new kind of heteropolysilicate anion Acta Crystallographica B37 1972-1978		1981	Molinello, Chavari, Liguria, Italy	0	293
0019903	Medaite	Nagashima M, Armbruster T (2010) Ardennite, tiragalloite and medaite: structural control of (As5+,V5+,Si4+)O4 tetrahedra in silicates Mineralogical Magazine 74 55-71	2010	Molinello, Val Graveglia, Liguria, Italy	0	293
0019904	Medaite	Nagashima M, Armbruster T (2010) Ardennite, tiragalloite and medaite: structural control of (As5+,V5+,Si4+)O4 tetrahedra in silicates Mineralogical Magazine 74 55-71	2010	Fianel, Val Ferrera, Graubunden, Switzerland	0	293

CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

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Powder Diffraction Data:

Geological EnvironmentHide

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Type Occurrence of MedaiteHide

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General Appearance of Type Material:

Small brown grains embedded in brownish veinlets, a few millimeters thick, cutting a black Mn ore made up
mainly of quartz and braunite. The grains reach 1.5 mm but are usually smaller. They are usually embedded in quartz.

Place of Conservation of Type Material:

Institute of Mineralogy, Milan, Mineral Museums of Universities of Rome and Oslo, Norway.

Geological Setting of Type Material:

Associated Minerals at Type Locality:

Reference:

Gramaccioli, C.M., Griffin, W.L., Mottana, A. (1982) Medaite, Mn6[VSi5O18(OH)], a new mineral and the first example of vanadatopentasilicate ion. American Mineralogist: 67: 85-89.

Synonyms of MedaiteHide

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Other Language Names for MedaiteHide

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Common AssociatesHide

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Associated Minerals Based on Photo Data:

Related Minerals - Strunz-mindat GroupingHide

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Other InformationHide

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Notes:

Insoluble in water, HCl, and HNO3.

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 MedaiteHide

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References for MedaiteHide

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Localities for MedaiteHide

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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.