Stichtite Mineral Data

Stichtite Mineral Data +

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General Stichtite Information

Chemical Formula:

Mg6Cr2(CO3)(OH)16·4(H2O)

Composition:

Molecular Weight = 654.01 gm

Magnesium 22.30 % Mg 36.98 % MgO

Chromium 15.90 % Cr 23.24 % Cr₂O₃

Hydrogen 3.70 % H 33.06 % H₂O

Carbon 1.84 % C 6.73 % CO₂

Oxygen 56.27 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Mg₆Cr₂(OH)₁₆(CO₃)·4(H₂O)

Environment:

Alteration product of serpentine.

IMA Status:

Valid Species (Pre-IMA) 1910

Locality:

Dundas, Tasmania. Link to MinDat.org Location Data.

Name Origin:

Named after Robert Sticht, director of a mining corporation.

Stichtite Image

Images:

Stichtite

Comments: Massive, fibrous, lavender-purple stichtite.
Location: Kaapsche Hoop, Barberton District, Mpumalanga Province, South Africa. Scale: 5x3x2 cm.
© John Betts - Fine Minerals

Stichtite Crystallography

Axial Ratios:

a:c = 1:7.50485

Cell Dimensions:

a = 6.18, c = 46.38, Z = 3; V = 1,534.05 Den(Calc)= 2.12

Crystal System:

Trigonal - Hexagonal ScalenohedralH-M Symbol (3 2/m) Space Group: R 3m

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

By Intensity(I/I_o): 7.8(1), 3.91(0.9), 2.6(0.4),

Physical Properties of Stichtite

Cleavage:

[0001] Perfect

Color:

Lilac, Light violet, Pink.

Density:

2.2

Diaphaniety:

Transparent to translucent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Encrustations - Forms crust-like aggregates on matrix.

Habit:

Micaceous - Platy texture with "flexible" plates.

Habit:

Nodular - Tuberose forms having irregular protuberances over the surface.

Hardness:

1.5-2 - Talc-Gypsum

Luminescence:

None.

Luster:

Vitreous (Glassy)

Magnetism:

Nonmagnetic

Streak:

pale violet blue

Optical Properties of Stichtite

Dichroism (e):

colorless.

Dichroism (w):

colorless.

Gladstone-Dale:

CI meas= 0.103 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= 0.069 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2495,KPDmeas= 0.2405,KC= 0.2679

Optical Data:

Uniaxial (+), w=1.516, e=1.542, bire=0.0260.

Calculated Properties of Stichtite

Electron Density:

r_electron=2.17 gm/cc
note: r_Stichtite=2.12 gm/cc.

Fermion Index

Fermion Index = 0.03788
Boson Index = 0.96212

Photoelectric:

PE_Stichtite= 4.01 barns/electron
U=PE_Stichtite x r_electron= 8.67 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Stichtite is Not Radioactive

Stichtite Classification

Dana Class:

16b.6.2.2 (16b)Carbonates - Hydroxyl or Halogen

(16b.6)Dana Type

(16b.6.2)Sjorgrenite-Hydrotalcite Group (Hydrotalcite Subgroup:Rhombohedral)

16b.6.2.1 Hydrotalcite Mg6Al2(CO3)(OH)16·4(H2O) R 3m 3 2/m

16b.6.2.2 Stichtite Mg6Cr2(CO3)(OH)16·4(H2O) R 3m 3 2/m

16b.6.2.3 Pyroaurite Mg6Fe2(CO3)(OH)16·4(H2O) R 3m 3 2/m

16b.6.2.4 Desautelsite Mg6Mn2(CO3)(OH)16·4(H2O) R 3m or R 3m Trig

Strunz Class:

V/E.03-20 V - Nitrates, Carbonates and Borates

V/E - Water-bearing carbonates with unfamiliar anions

V/E.03 - Hydrotalcite group

V/E.03-10 Hydrotalcite Mg6Al2(CO3)(OH)16·4(H2O) R 3m 3 2/m

V/E.03-20 Stichtite Mg6Cr2(CO3)(OH)16·4(H2O) R 3m 3 2/m

V/E.03-30 Pyroaurite Mg6Fe2(CO3)(OH)16·4(H2O) R 3m 3 2/m

V/E.03-40 Desautelsite Mg6Mn2(CO3)(OH)16·4(H2O) R 3m or R 3m Trig

V/E.03-50 Takovite Ni6Al2(OH)16(CO3,OH)·4(H2O) R 3m 3 2/m

V/E.03-60 Reevesite Ni6Fe2(CO3)(OH)16·4(H2O) R 3m 3 2/m

V/E.03-70 Comblainite Ni6Co2(CO3)(OH)16·4(H2O) R 3m 3 2/m

V/E.03-80 Sergeevite Ca2Mg11(CO3)9(HCO3)4(OH)4·6(H2O) R 32 3 2

Other Stichtite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

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Stichtite

Mg6Cr2(CO3)(OH)16·4(H2O)
Dana No: 16b.6.2.2 Strunz No: V/E.03-20
Locality:

Notes: