Talmessite Mineral Data

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)

IMA Status:

Approved IMA 1960

Locality:

Link to MinDat.org Location Data.

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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drag2 - RMB Resize/Rotate
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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

Diaphaniety:

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= 0.027 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1887,KPDmeas= 0.2045,KC= 0.1939

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:

r_electron=3.51 gm/cc
note: r_Talmessite=3.63 gm/cc.

Fermion Index

Fermion Index = 0.00625
Boson Index = 0.99375

Photoelectric:

PE_Talmessite= 26.60 barns/electron
U=PE_Talmessite x r_electron= 93.26 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Talmessite is Not Radioactive

Talmessite Classification

Dana Class:

40.2.2.5 (40)Hydrated Phosphates, etc

(40.2)where A++ (B++)2 (XO4) · x(H2O)

(40.2.2)Fairfieldite Subgroup (Triclinic: P1¯)

40.2.2.1 Fairfieldite Ca2(Mn,Fe)(PO4)2·2(H2O) P1 1

40.2.2.2 Messelite Ca2(Fe,Mn)(PO4)2·2(H2O) P1 1

40.2.2.3 Collinsite Ca2(Mg,Fe)(PO4)2·2(H2O) P1 1

40.2.2.4 Cassidyite Ca2(Ni,Mg)(PO4)2·2(H2O) P1 1

40.2.2.5 Talmessite Ca2Mg(AsO4)2·2(H2O) P1 1

40.2.2.6 Gaitite Ca2Zn(AsO4)2·2(H2O) P1 1

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

40.2.2.8 Parabrandtite Ca2Mn(AsO4)·2(H2O) P1,P 1 Tri

40.2.2.9 Hillite! Ca2(Zn,Mg)[PO4]2·2(H2O) P1 1

Strunz Class:

VII/C.17-50 VII - Phosphates, Arsenates and Vanadates

VII/C - Water-bearing phosphates without unfamiliar anions, cations of medium and big size: Fe, Mn, Zn, Mg and Ca, (NH4)1+

VII/C.17 - Collinsite - Wendwilsonite series

VII/C.17-10 Collinsite Ca2(Mg,Fe)(PO4)2·2(H2O) P1 1

VII/C.17-15 Hillite! Ca2(Zn,Mg)[PO4]2·2(H2O) P1 1

VII/C.17-20 Messelite Ca2(Fe,Mn)(PO4)2·2(H2O) P1 1

VII/C.17-30 Fairfieldite Ca2(Mn,Fe)(PO4)2·2(H2O) P1 1

VII/C.17-40 Cassidyite Ca2(Ni,Mg)(PO4)2·2(H2O) P1 1

VII/C.17-50 Talmessite Ca2Mg(AsO4)2·2(H2O) P1 1

VII/C.17-60 Gaitite Ca2Zn(AsO4)2·2(H2O) P1 1

VII/C.17-70 Parabrandtite Ca2Mn(AsO4)·2(H2O) P1,P 1 Tri

VII/C.17-80 Roselite-beta Ca2(Co,Mg)(AsO4)2·2(H2O) P 1 or P1 Tri

VII/C.17-90 Wendwilsonite Ca2(Mg,Co)(AsO4)2·2(H2O) P 2₁/c 2/m

VII/C.17-100 Roselite Ca2(Co,Mg)(AsO4)2·2(H2O) P 2₁/c 2/m

VII/C.17-110 Brandtite Ca2(Mn,Mg)(AsO4)2·2(H2O) P 2₁/c 2/m

VII/C.17-120 Zincroselite Ca2Zn(AsO4)2·2(H2O) P 2₁/c 2/m

Other Talmessite Information

References:

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 -Google Images 5 -Google Scholar 6 -Handbook of Mineralogy (UofA) 7 -MinDAT 8 -MinMax(Deutsch) 9 -MinMax(English) 10 -Mineralienatlas (Deutsch) 11 -QUT Mineral Atlas 12 - WWW-MINCRYST 13 -École des Mines de Paris

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

Talmessite

Ca2Mg(AsO4)2·2(H2O)
Dana No: 40.2.2.5 Strunz No: VII/C.17-50
Locality:

Notes: