Dorrite Mineral Data

Dorrite Mineral Data +

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General Dorrite Information

Chemical Formula:

Ca2Mg2Fe+++4(Al,Fe+++)4Si2O20

Composition:

Molecular Weight = 893.97 gm

Calcium 8.97 % Ca 12.55 % CaO

Magnesium 5.44 % Mg 9.02 % MgO

Aluminum 6.04 % Al 11.41 % Al₂O₃

Iron 37.48 % Fe 53.59 % Fe₂O₃

Silicon 6.28 % Si 13.44 % SiO₂

Oxygen 35.79 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ca₂Mg₂Fe³⁺₆Al₂Si₂O₂₀

Environment:

Occurs in a paralava (pyrometamorhic melt rock) formed from burning coal beds.

IMA Status:

Approved IMA 1988

Locality:

Druham ranch, 25 km S of Gillette in the Powder River Basin, Wyoming. USA. Link to MinDat.org Location Data.

Name Origin:

Named for John A. Dorr (1922-1986), University of Michigan.

Dorrite Image

Images:

Dorrite

Comments: Dark brown micaceous dorrite (arrow) on matrix.
Location: Eicher, Sattel, Baden-Wurttemberg, Germany. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Dorrite Crystallography

Axial Ratios:

a:b:c =0.964:1:0.8276

Cell Dimensions:

a = 10.505, b = 10.897, c = 9.019, Z = 2; alpha = 106.26°, beta = 95.16°, gamma = 124.75° V = 811.06 Den(Calc)= 3.66

Crystal System:

TriclinicSpace Group: P1,P 1

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

By Intensity(I/I_o): 2.971(1), 2.515(0.8), 2.558(0.8),

Physical Properties of Dorrite

Cleavage:

[001] Distinct, [010] Distinct

Color:

Brownish black, Dark brown, Reddish brown.

Diaphaniety:

Subopaque

Fracture:

Irregular - Flat surfaces (not cleavage) fractured in an irregular pattern.

Habit:

Anhedral Grains - Granular minerals without the expression of crystal shapes

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Hardness:

5 - Apatite

Luster:

Sub Metallic

Optical Properties of Dorrite

Gladstone-Dale:

CI calc= 0.133 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2295,KC= 0.2648

Optical Data:

Biaxial (-), a=1.82, b=1.84, g=1.86, bire=0.0400, 2V(Calc)=88, 2V(Meas)=90.

Pleochroism (x):

red-orange brown.

Pleochroism (y):

yellowish brown.

Pleochroism (z):

greenish brown.

Calculated Properties of Dorrite

Electron Density:

r_electron=3.55 gm/cc
note: r_Dorrite=3.66 gm/cc.

Fermion Index

Fermion Index = 0.01661
Boson Index = 0.98339

Photoelectric:

PE_Dorrite= 12.91 barns/electron
U=PE_Dorrite x r_electron= 45.87 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Dorrite is Not Radioactive

Dorrite Classification

Dana Class:

69.2.1a.2 (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.14-40 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 Dorrite Information

References:

NAME( Dana8) PHYS. PROP.(Dana8) OPTIC PROP.(Dana8)

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Dorrite

Ca2Mg2Fe+++4(Al,Fe+++)4Si2O20
Dana No: 69.2.1a.2 Strunz No: VIII/F.14-40
Locality:

Notes: