Medaite Mineral Data

General Medaite Information

Chemical Formula:

(Mn,Ca)6(V+++++,As)Si5O18(OH)

Composition:

Molecular Weight = 827.82 gm

Calcium 0.97 % Ca 1.35 % CaO

Manganese 38.49 % Mn 49.70 % MnO

Vanadium 4.92 % V 8.79 % V₂O₅

Silicon 16.96 % Si 36.29 % SiO₂

Arsenic 1.81 % As 2.78 % As₂O₅

Hydrogen 0.12 % H 1.09 % H₂O

Oxygen 36.72 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Mn²⁺_5.8Ca_0.2V⁵⁺_0.8As_0.2Si₅O₁₈(OH)

Environment:

Formed at low temperatures and low H2O fugacity in veinlets cutting manganese ores.

IMA Status:

Approved IMA 1980

Locality:

From the Molinello manganese mine, near Chiavari, Val Graveari, Val Graveglia, Liuria, Italy. Link to MinDat.org Location Data.

Name Origin:

Named for Dr. Francesco Meda (1926-1977), an amateur mineralogist from Turin, Italy.

Name Pronunciation:

Medaite

Synonym:

ICSD 26908

PDF 36-443

Medaite Image

Images:

Medaite

Comments: Orange crystalline medaite crust.
Location: Molinello Mine, near Chiavari, Liguria, Italy. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Medaite Crystallography

Axial Ratios:

a:b:c =0.2318:1:0.2617

Cell Dimensions:

a = 6.712, b = 28.948, c = 7.578, Z = 4; beta = 95.4° V = 1,465.86 Den(Calc)= 3.75

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2₁/n

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.259(1), 3.159(0.83), 3.097(0.7),

Crystal Structure:

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drag2 - RMB Resize/Rotate
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Gramaccioli C M , Liborio G , Pilati T , Acta Crystallographica, Section B , 37 (1981) p.1972-1978, Structure of medaite, Mn6[VSi5O18(OH)]: The presence of a new kind of, heteropolysilicate anion, Locality: Molinello, Chavari, Liguria, Italy, Note: anisoB s from ICSD

Physical Properties of Medaite

Cleavage:

{100} Good, {001} Parting

Color:

Brownish red.

Density:

3.7

Diaphaneity:

Transparent

Habit:

Aggregates - Made of numerous individual crystals or clusters.

Habit:

Granular - Generally occurs as anhedral to subhedral crystals in matrix.

Luster:

Subadamantine

Streak:

yellow white

Optical Properties of Medaite

Gladstone-Dale:

CI meas= 0.012 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.025 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2089,KPDmeas= 0.2117,KC= 0.2143
Ncalc = 1.79 - 1.8

Optical Data:

Biaxial (+), a=1.77, b=1.78, g=1.8, bire=0.0300, 2V(Calc)=72, 2V(Meas)=71.

Pleochroism (x):

faint orange.

Pleochroism (y):

pale orange.

Pleochroism (z):

light orange.

Calculated Properties of Medaite

Electron Density:

Bulk Density (Electron Density)=3.55 gm/cc
note: Specific Gravity of Medaite =3.70 gm/cc.

Fermion Index:

Fermion Index = 0.0082345821
Boson Index = 0.9917654179

Photoelectric:

PE_Medaite= 12.87 barns/electron
U=PE_Medaite x rElectron Density= 45.66 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Medaite is Not Radioactive

Medaite Classification

Dana Class:

57.04.01.01 (57)Sorosilicate Insular Si3O10 and Larger Noncyclic Groups

(57.04)with groups with 6 or more tetrahedra

(57.04.01)Dana Group

57.04.01.01 Medaite (Mn,Ca)6(V,As)Si5O18(OH) P 2₁/n 2/m

Strunz Class:

09.BJ.30 09 - SILICATES (Germanates)

09.B - Sorosilicates

09.BJ -Sorosilicates with Si3O10, Si4O11, etc

09.BJ.30 Medaite (Mn,Ca)6(V,As)Si5O18(OH) P 2₁/n 2/m

Other Medaite Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Medaite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info
15 - WWW-MINCRYST

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Ask about Medaite here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

Print or Cut-and-Paste your Medaite Specimen Label here :

Medaite

(Mn,Ca)6(V+++++,As)Si5O18(OH)
Dana No: 57.04.01.01 Strunz No: 09.BJ.30
Locality:

Notes: