Talmessite Mineral Data

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General Talmessite Information

Chemical Formula:

Ca2Mg(AsO4)2•2(H2O)

Composition:

Molecular Weight = 418.33 gm

Calcium 19.16 % Ca 26.81 % CaO

Magnesium 5.81 % Mg 9.63 % MgO

Arsenic 35.82 % As 54.94 % As₂O₅

Hydrogen 0.96 % H 8.61 % H₂O

Oxygen 38.25 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ca₂Mg(AsO₄)₂•2(H₂O)

Environment:

Secondary species formed typically in the oxidized zone of some hydrothermal mineral deposits, an alteration product of realgar, orpiment, or Cu-Ni arsenides.

IMA Status:

Approved IMA 1960

Locality:

Talmessi mine, 35 km west of Anarak, Iran. In the Arhbar (Aghbar) and A¨it Ahmane mines, Bou Azzer district, Morocco. Link to MinDat.org Location Data.

Name Origin:

Named for the locality.

Name Pronunciation:

Talmessite + Pronunciation

Synonym:

ICSD 200008

PDF 38-451

Talmessite Image

Images:

Talmessite

Comments: Pale green, crystalline aggregates of talmessite on reddish, hematite-stained calcite.
Location: Ourlil, Bou Azzer, Anti Atlas Mts., Morocco. Scale: Crystal size 4 mm.
© John Veevaert

Images:

Talmessite

Comments: Translucent nearly colorless talmessite microcrystals.
Location: Old Gold Hill Mine, Tooele County, Utah, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Images:

Talmessite

Comments: Vivid pink-colored talmessite crystalline aggregates scattered on matrix.
Location: Bou Azzer, Morocco. Scale: Picture size 2 cm.
© Sandro Maggia/Minernet.it

Talmessite Crystallography

Axial Ratios:

a:b:c =0.7659:1:0.723

Cell Dimensions:

a = 5.89, b = 7.69, c = 5.56, Z = 1; alpha = 112.633°, beta = 70.817°, gamma = 119.417° V = 191.23 Den(Calc)= 3.63

Crystal System:

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

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

By Intensity(I/I_o): 2.77(1), 3.07(1), 3.21(0.8),

Crystal Structure:

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Catti M , Ferraris G , Ivaldi G , Bulletin de Mineralogie , 100 (1977) p.230-236, Hydrogen bonding in the crystalline state. Structure of talmessite,, Ca2(Mg,Co)(AsO4)2*2H2O, and crystal chemistry of related minerals, Locality: Bou-Azzer, Morocco

Physical Properties of Talmessite

Color:

Colorless, White, Light green.

Density:

3.2 - 3.5, Average = 3.35

Diaphaneity:

Transparent to Translucent

Hardness:

5 - Apatite

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Talmessite

Gladstone-Dale:

CI meas= -0.055 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= -0.015 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1968,KPDmeas= 0.2045,KC= 0.1939
Ncalc = 1.62 - 1.68

Optical Data:

Biaxial (-), a=1.672, b=1.685, g=1.698, bire=0.0260, 2V(Calc)=88, 2V(Meas)=90.

Calculated Properties of Talmessite

Electron Density:

Bulk Density (Electron Density)=3.36 gm/cc
note: Specific Gravity of Talmessite =3.48 gm/cc.

Fermion Index:

Fermion Index = 0.0062537058
Boson Index = 0.9937462942

Photoelectric:

PE_Talmessite= 26.60 barns/electron
U=PE_Talmessite x rElectron Density= 89.40 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Talmessite is Not Radioactive

Talmessite Classification

Dana Class:

40.02.02.05 (40)Hydrated Phosphates, etc

(40.02)where A++ (B++)2 (XO4) · x(H2O)

(40.02.02)Fairfieldite Subgroup (Triclinic: P-1¯)

40.02.02.01 Fairfieldite Ca2(Mn,Fe)(PO4)2•2(H2O) P1 1

40.02.02.02 Messelite Ca2(Fe,Mn)(PO4)2•2(H2O) P1 1

40.02.02.03 Collinsite Ca2(Mg,Fe)(PO4)2•2(H2O) P1 1

40.02.02.04 Cassidyite Ca2(Ni,Mg)(PO4)2•2(H2O) P1 1

40.02.02.05 Talmessite Ca2Mg(AsO4)2•2(H2O) P1 1

40.02.02.06 Gaitite Ca2Zn(AsO4)2•2(H2O) P1 1

40.02.02.07 Roselite-beta Ca2(Co,Mg)(AsO4)2•2(H2O) P 1 or P1 Tri

40.02.02.08 Parabrandtite Ca2Mn(AsO4)•2(H2O) P1,P 1 Tri

40.02.02.09 Hillite! Ca2(Zn,Mg)[PO4]2•2(H2O) P1 1

40.02.02.10 Nickeltalmessite! Ca2Ni(AsO4)2•2H2O P 1

Strunz Class:

08.CG.05 08 - PHOSPHATES, ARSENATES, VANADATES

08.C - Phosphates without Additional Anions, with H2O

08.CG -With large and medium-sized cations, RO4:H2O = 1:1

08.CG.05 Collinsite Ca2(Mg,Fe)(PO4)2•2(H2O) P1 1

08.CG.05 Gaitite Ca2Zn(AsO4)2•2(H2O) P1 1

08.CG.05 Cassidyite Ca2(Ni,Mg)(PO4)2•2(H2O) P1 1

08.CG.05 Fairfieldite Ca2(Mn,Fe)(PO4)2•2(H2O) P1 1

08.CG.05 Messelite Ca2(Fe,Mn)(PO4)2•2(H2O) P1 1

08.CG.05 Parabrandtite Ca2Mn(AsO4)•2(H2O) P1,P 1 Tri

08.CG.05 Uranophane-beta Ca[(UO2)SiO3(OH)]2•(H2O) P 2₁/a 2/m

08.CG.05 Talmessite Ca2Mg(AsO4)2•2(H2O) P1 1

08.CG.05 Hillite! Ca2(Zn,Mg)[PO4]2•2(H2O) P1 1

Other Talmessite Information

References:

NAME( AntBidBlaNic4) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

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

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Ask about Talmessite here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

Print or Cut-and-Paste your Talmessite Specimen Label here :

Talmessite

Ca2Mg(AsO4)2•2(H2O)
Dana No: 40.02.02.05 Strunz No: 08.CG.05
Locality:

Notes: