Ahlfeldite Mineral Data

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General Ahlfeldite Information

Chemical Formula:

(Ni,Co)SeO3•2(H2O)

Composition:

Molecular Weight = 221.74 gm

Cobalt 6.64 % Co 8.45 % CoO

Nickel 19.85 % Ni 25.26 % NiO

Hydrogen 1.82 % H 16.25 % H₂O

Selenium 35.61 % Se 50.04 % SeO₂

Oxygen 36.08 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ni_0.75Co_0.25(SeO₃)•2(H₂O)

Environment:

Formed as an alteration product of penroseeite and other selenides.

IMA Status:

Valid Species (Pre-IMA) 1935

Locality:

Bolivia, Potosí, Colquechaca Link to MinDat.org Location Data.

Name Origin:

Named for Federico Ahlfeld (1892-192), German-Bolivian geologist and mineralogist who studied Bolivian minerals.

Synonym:

ICSD 69220

PDF 25-1233

Ahlfeldite Image

Images:

Ahlfeldite

Comments: Green encrustations of ahlfeldite on matrix.
Location: Mina El Dragon, Potosi, Bolivia. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Ahlfeldite Crystallography

Axial Ratios:

a:b:c =0.8595:1:0.734

Cell Dimensions:

a = 7.53, b = 8.76, c = 6.43, Z = 4; beta = 99.083° V = 418.82 Den(Calc)= 3.52

Crystal System:

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

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

By Intensity(I/I_o): 5.69(1), 3.426(0.8), 2.992(0.75),

Forms:

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Forms: ( 0 2 1) ( 1 1 0) ( 1 0 3) ( 1 0 1) ( 0 1 1)

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Crystal Structure:

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Wildner M , Neues Jahrbuch fur Mineralogie, Monatshefte , 1990 (1990) p.353-362, Crystal structure refinements of synthetic cobaltomenite (CoSeO3*2H2O), and ahlfeldite (NiSeO3*2H2O)

Physical Properties of Ahlfeldite

Cleavage:

{110} Distinct, {103} Distinct

Color:

Pink brown, Apple green, Red.

Density:

3.37

Diaphaneity:

Transparent

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

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

Hardness:

2-2.5 - Gypsum-Finger Nail

Luster:

Vitreous (Glassy)

Streak:

light green

Optical Properties of Ahlfeldite

Gladstone-Dale:

CI meas= -0.04 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.004 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2115,KPDmeas= 0.2209,KC= 0.2124, Ncalc =

Optical Data:

Biaxial (-), a=1.703, b=1.744, g=1.786, bire=0.0830, 2V(Calc)=88, 2V(Meas)=85. Dispersion r < v.

NCalc= 1.75 - from Gladstone-Dale relationship (KC = 0.2124) where Ncalc=Dcalc*KC+1
NCalc= 1.72 - from Gladstone-Dale relationship (KC = 0.2124) where Ncalc=Dmeas*KC+1 KPDcalc= 0.2115,KPDmeas= 0.2209,KC= 0.2124, Ncalc =

Pleochroism (x):

very pale green.

Pleochroism (y):

pale green.

Pleochroism (z):

green.

Calculated Properties of Ahlfeldite

Electron Density:

ρ_electron=3.36 gm/cc
note: r_Ahlfeldite=3.52 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

Photoelectric:

PE_Ahlfeldite= 36.70 barns/electron
U=PE_Ahlfeldite x r_electron= 123.17 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Ahlfeldite is Not Radioactive

Ahlfeldite Classification

Dana Class:

34.02.03.03 (34)Selenites - Tellurites - Sulfites

(34.02)as A++ XO3 • x(H2O)

(34.02.03)Chalcomenite Group (Monoclinic)

34.02.03.01 Clinochalcomenite CuSeO3•2(H2O) P 2₁/n 2/m

34.02.03.02 Cobaltomenite CoSeO3•2(H2O) P 2₁/n 2/m

34.02.03.03 Ahlfeldite (Ni,Co)SeO3•2(H2O) P 2₁/m 2/m

Strunz Class:

04.JH.10 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.J - Arsenites, Antimonites, Bismuthites, Sulfites,

04.JH -Selenites without additional anions, with H2O

04.JH.05 Chalcomenite CuSeO3•2(H2O) P 2₁2₁2₁ 2 2 2

04.JH.10 Ahlfeldite (Ni,Co)SeO3•2(H2O) P 2₁/m 2/m

04.JH.10 Ahlfeldite CuSeO3•2(H2O) P 2₁/n 2/m

04.JH.10 Ahlfeldite CoSeO3•2(H2O) P 2₁/n 2/m

04.JH.15 Mandarinoite Fe2Se3O9•6(H2O) P 2₁/c 2/m

04.JH.20 Orlandiite! Pb3(Cl,OH)4(SeO3)•(H2O) P1 1

04.JH.25 Larisaite! Na(H3O)(UO2)3(SeO3)2O2•4(H2O) Pm 2

Other Ahlfeldite Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Dana8)

See Also:

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

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Ahlfeldite

(Ni,Co)SeO3•2(H2O)
Dana No: 34.02.03.03 Strunz No: 04.JH.10
Locality:

Notes: