Robertsite Mineral Data

Robertsite Mineral Data +

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General Robertsite Information

Chemical Formula:

Ca6Mn+++9(PO4)9O6(H2O)6·3(H2O)

Composition:

Molecular Weight = 1,739.69 gm

Calcium 13.82 % Ca 19.34 % CaO

Manganese 28.42 % Mn 36.70 % MnO

Phosphorus 16.02 % P 36.72 % P₂O₅

Hydrogen 0.35 % H 3.11 % H₂O

Oxygen 41.39 % O

______ ______

100.00 % 95.86 % = TOTAL OXIDE

Empirical Formula:

Ca₆Mn²⁺₉(PO₄)₉O₆·3(H₂O)

IMA Status:

Approved IMA 1974

Locality:

Tip Top mine, Custer County, South Dakota, USA. Link to MinDat.org Location Data.

Name Origin:

Named for Willard Lincoln Roberts (1923-1987), mineralogist, South Dakota School of Mines.

Robertsite Image

Images:

Robertsite Carbonate-hydroxylapatite Apatite

Comments: Black crystals of Robertsite on pink carbonate-hydroxylapatite.
Location: Tip Top mine, Custer, Custer County, South Dakota, USA. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Robertsite Crystallography

Axial Ratios:

a:b:c =0.8888:1:0.5785

Cell Dimensions:

a = 17.36, b = 19.53, c = 11.3, Z = 4; beta = 96° V = 3,810.17 Den(Calc)= 3.03

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: A2/a

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

By Intensity(I/I_o): 8.63(1), 2.74(0.6), 5.61(0.5),

Physical Properties of Robertsite

Cleavage:

[100] Good

Color:

Blood red, Brownish black, Dark red, Reddish brown, Black.

Density:

3.17

Diaphaniety:

Translucent to Opaque

Habit:

Aggregates - Made of numerous individual crystals or clusters.

Habit:

Felted - Occurs as minute crystalling aggregates with the form of felt material.

Hardness:

3.5 - Copper Penny

Luster:

Adamantine

Streak:

brown

Optical Properties of Robertsite

Gladstone-Dale:

CI meas= -0.332 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.393 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2657,KPDmeas= 0.2539,KC= 0.1907

Optical Data:

Biaxial (-), a=1.775, b=1.82, g=1.82, bire=0.0450, 2V(Calc)=0, 2V(Meas)=8.

Calculated Properties of Robertsite

Electron Density:

r_electron=3.08 gm/cc
note: r_Robertsite=3.17 gm/cc.

Fermion Index

Fermion Index = 0.00038
Boson Index = 0.99962

Photoelectric:

PE_Robertsite= 9.75 barns/electron
U=PE_Robertsite x r_electron= 30.07 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Robertsite is Not Radioactive

Robertsite Classification

Dana Class:

42.8.4.2 (42)Hydrated Phosphates, etc., Containing Hydroxyl or Halogen

(42.8)where (AB)7 (XO4)4 Zq · x(H2O)

(42.8.4)Dana Group

42.8.4.1 Mitridatite Ca2Fe3(PO4)3O2·3(H2O) A2/a 2/m

42.8.4.2 Robertsite Ca6Mn9(PO4)9O6(H2O)6·3(H2O) A2/a 2/m

42.8.4.3 Arseniosiderite Ca2Fe3(AsO4)3O2·3(H2O) A2/a 2/m

Strunz Class:

VII/D.30-50 VII - Phosphates, Arsenates and Vanadates

VII/D - Water-bearing phosphates with unfamiliar anions, cations of very big and medium size: Al, Mg and Ca, Na, K

VII/D.30 - Mitridatite series

VII/D.30-10 Xanthoxenite Ca4Fe2(PO4)4(OH)2·3(H2O) P1 1

VII/D.30-20 Kolfanite Ca2Fe3O2(AsO4)3·2(H2O) A2/a 2/m

VII/D.30-30 Mitridatite Ca2Fe3(PO4)3O2·3(H2O) A2/a 2/m

VII/D.30-40 Arseniosiderite Ca2Fe3(AsO4)3O2·3(H2O) A2/a 2/m

VII/D.30-45 Sailaufite! Ca2Mn3O2(AsO4)2(CO3)·3(H2O) Cm m

VII/D.30-50 Robertsite Ca6Mn9(PO4)9O6(H2O)6·3(H2O) A2/a 2/m

VII/D.30-60 Pararobertsite Ca2Mn3(PO4)3O2·3(H2O) P 2₁/c 2/m

Other Robertsite Information

References:

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

See Also:

Links to other databases for Robertsite :
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 -École des Mines de Paris

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Robertsite

Ca6Mn+++9(PO4)9O6(H2O)6·3(H2O)
Dana No: 42.8.4.2 Strunz No: VII/D.30-50
Locality:

Notes: