Welshite Mineral Data

Welshite Mineral Data +

General Welshite Information

Chemical Formula:

Ca2Mg4(Mn,Fe)Sb+++++2O2[Si3Be2O18]

Composition:

Molecular Weight = 880.60 gm

Calcium 9.10 % Ca 12.74 % CaO

Magnesium 10.49 % Mg 17.39 % MgO

Manganese 3.74 % Mn 4.83 % MnO

Beryllium 1.74 % Be 4.83 % BeO

Aluminum 2.14 % Al 4.05 % Al₂O₃

Iron 5.07 % Fe 0.82 % FeO / 6.35 % Fe₂O₃

Silicon 8.93 % Si 19.10 % SiO₂

Antimony 20.74 % Sb 27.55 % Sb₂O₅

Arsenic 1.70 % As 2.25 % As₂O₃

Oxygen 36.34 % O

______ ______

100.00 % 99.91 % = TOTAL OXIDE

Empirical Formula:

Ca₂Mg_3.8Mn²⁺_0.6Fe²⁺_0.1Sb_1.5O₂Si_2.8Be_1.7Fe³⁺_0.7Al_0.7As_0.2O₁₈

IMA Status:

Approved IMA 1978

Locality:

Link to MinDat.org Location Data.

Welshite Image

Images:

Welshite

Comments: Deep red, prismatic crystal of welshite in matrix.
Location: Langban, Varmland, Sweden. Scale: Crystal size 1.5 mm.
© Tom Loomis / Dakota Matrix

Welshite Crystallography

Axial Ratios:

a:b:c =0.9616:1:0.8267

Cell Dimensions:

a = 10.28, b = 10.69, c = 8.838, Z = 2; alpha = 106.1°, beta = 96.3°, gamma = 124° V = 768.94 Den(Calc)= 3.80

Crystal System:

Triclinic - PinacoidalH-M Symbol ( 1) Space Group: P1

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

By Intensity(I/I_o): 2.53(1), 2.91(0.7), 7.324(0.7),

Physical Properties of Welshite

Cleavage:

None

Color:

Brown, Reddish black, Orange brown, Deep tan.

Density:

3.77

Diaphaniety:

Subtranslucent to Opaque

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Hardness:

6 - Orthoclase

Luster:

Subadamantine

Streak:

light brown

Optical Properties of Welshite

Gladstone-Dale:

CI meas= -0.097 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.089 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2158,KPDmeas= 0.2175,KC= 0.1982

Optical Data:

Biaxial (+), a=1.81, b=1.83, , 2V(Meas)=45.

Calculated Properties of Welshite

Electron Density:

r_electron=3.62 gm/cc
note: r_Welshite=3.80 gm/cc.

Fermion Index

Fermion Index = 0.03342
Boson Index = 0.96658

Photoelectric:

PE_Welshite= 69.53 barns/electron
U=PE_Welshite x r_electron= 251.78 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Welshite is Not Radioactive

Welshite Classification

Dana Class:

69.2.1a.7 (69)Inosilicate Chains with Side Branches or Loops

(69.2)with P>2

(69.2.1a)Aenigmatite and related species (Aenigmatite subgroup)

69.2.1a.1 Aenigmatite Na2Fe5TiSi6O20 P1 1

69.2.1a.2 Dorrite Ca2Mg2Fe4(Al,Fe)4Si2O20 P1,P 1 Tri

69.2.1a.3 Hogtuvaite (Ca,Na)2(Fe,Fe,Ti,Mg,Mn)6(Si,Be,Al)6O20 P1 1

69.2.1a.4 Krinovite NaMg2CrSi3O10 P1 1

69.2.1a.5 Rhonite Ca2(Mg,Fe,Fe,Ti)6(Si,Al)6O20 P1 1

69.2.1a.6 Serendibite Ca2(Mg,Al)6(Si,Al,B)6O20 P1 1

69.2.1a.7 Welshite Ca2Mg4(Mn,Fe)Sb2O2[Si3Be2O18] P1 1

69.2.1a.8 Wilkinsonite Na2Fe4Fe2Si6O20 P1 1

69.2.1a.9 IMA2002-009a! Ca2Fe4FeTiSi4BeAlO20 P1 1

Strunz Class:

VIII/F.14-70 VIII - Silicates

VIII/F - Inosilicates (chain and band) modified double chains

VIII/F.14 - Aenigmatite group

VIII/F.14-10 Krinovite NaMg2CrSi3O10 P1 1

VIII/F.14-20 Aenigmatite Na2Fe5TiSi6O20 P1 1

VIII/F.14-30 Wilkinsonite Na2Fe4Fe2Si6O20 P1 1

VIII/F.14-35 Hogtuvaite (Ca,Na)2(Fe,Fe,Ti,Mg,Mn)6(Si,Be,Al)6O20 P1 1

VIII/F.14-40 Dorrite Ca2Mg2Fe4(Al,Fe)4Si2O20 P1,P 1 Tri

VIII/F.14-50 Rhonite Ca2(Mg,Fe,Fe,Ti)6(Si,Al)6O20 P1 1

VIII/F.14-60 Serendibite Ca2(Mg,Al)6(Si,Al,B)6O20 P1 1

VIII/F.14-70 Welshite Ca2Mg4(Mn,Fe)Sb2O2[Si3Be2O18] P1 1

Other Welshite Information

References:

PHYS. PROP.(AmMin, Vol 87, p 358) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

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Welshite

Ca2Mg4(Mn,Fe)Sb+++++2O2[Si3Be2O18]
Dana No: 69.2.1a.7 Strunz No: VIII/F.14-70
Locality:

Notes: