Medaite Mineral Data

Medaite Mineral Data +

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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.

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),

Physical Properties of Medaite

Cleavage:

[100] Good, [001] Parting

Color:

Brownish red.

Density:

3.7

Diaphaniety:

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

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:

r_electron=3.55 gm/cc
note: r_Medaite=3.70 gm/cc.

Fermion Index

Fermion Index = 0.00823
Boson Index = 0.99177

Photoelectric:

PE_Medaite= 12.87 barns/electron
U=PE_Medaite x r_electron= 45.66 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Medaite is Not Radioactive

Medaite Classification

Dana Class:

57.4.1.1 (57)Sorosilicate Insular Si3O10 and Larger Noncyclic Groups

(57.4)with groups with 6 or more tetrahedra

(57.4.1)Dana Group

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

Strunz Class:

VIII/C.34-14 VIII - Silicates

VIII/C - Sorosilicates, other group-silicates

VIII/C.34 - Ardennite - Orientite series

VIII/C.34-10 Ardennite (Mn,Ca,Mg)4(Al,Mg,Fe)6(SiO4)2(Si3O10)(AsO4,VO4)(OH)6 Pnmm 2/m 2/m 2/m

VIII/C.34-14 Medaite (Mn,Ca)6(V,As)Si5O18(OH) P 2₁/n 2/m

VIII/C.34-16 Saneroite Na2(Mn,Fe)10Si11VO34(OH)4 P1 1

VIII/C.34-20 Orientite Ca2MnMn2Si3O10(OH)4 C mcm 2/m 2/m 2/m

Other Medaite Information

References:

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

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

Medaite

(Mn,Ca)6(V+++++,As)Si5O18(OH)
Dana No: 57.4.1.1 Strunz No: VIII/C.34-14
Locality:

Notes: