Ralstonite Mineral Data

Ralstonite Mineral Data +

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General Ralstonite Information

Chemical Formula:

NaxMgxAl2-x(F,OH)6·(H2O)

Composition:

Molecular Weight = 192.14 gm

Sodium 5.98 % Na 8.06 % Na₂O

Magnesium 6.32 % Mg 10.49 % MgO

Aluminum 21.06 % Al 39.80 % Al₂O₃

Hydrogen 2.10 % H 18.75 % H₂O

Oxygen 24.98 % O

Fluorine 39.55 % F 39.55 % F

- % F -16.65 % -O=F₂

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Na_0.5Mg_0.5Al_1.5F₄(OH)₂·(H₂O)

Environment:

Alteration product of cryolite.

IMA Status:

Valid Species (Pre-IMA) 1871

Locality:

Ivigtut, Greenland. Link to MinDat.org Location Data.

Name Origin:

Named for J. Grier Ralston (1851-1880) of Norristown, Pennsylvania, USA, who first observed the mineral.

Synonym:

ICSD 31345

PDF 45-1331

Ralstonite Image

Images:

Ralstonite Cryolite

Comments: Massive cryolite with solution cavities lined with octahedral ralstonite crystals.
Location: Ivigtut, Greenland. Scale: Picture size 0.5 cm.
© John Veevaert

Images:

Ralstonite Gjerdingenite-Fe

Comments: SEM photomicrograph of gjerdingenite-Fe. The mineral is dusted with tiny crystals of two phases. At high magnification, one of them is seen to form cubes and is probably ralstonite.
Location: Gjerdingselva, Lunner, Oppland, Oslo Region, Norway. Scale: Crystal length 0.5 mm.
© Canadian Mineralogist

Ralstonite Crystallography

Cell Dimensions:

a = 9.89, Z = 8; V = 967.36 Den(Calc)= 2.64

Crystal System:

Isometric - HexoctahedralH-M Symbol (4/m 3 2/m) Space Group: F d3m

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

By Intensity(I/I_o): 5.74(1), 1.765(0.85), 2.88(0.75),

Crystal Structure:

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Pabst A , American Mineralogist , 24 (1939) p.566-576, Formula and structure of ralstonite

View Additional jPOWD Structure files for Ralstonite
[1]

Physical Properties of Ralstonite

Cleavage:

[???] Perfect, [???] Perfect, [???] Perfect

Color:

Colorless, White.

Density:

2.55

Diaphaniety:

Transparent to translucent

Fracture:

Brittle - Uneven - Very brittle fracture producing uneven fragments.

Hardness:

4.5 - Between Fluorite and Apatite

Luminescence:

Non-fluorescent.

Luster:

Vitreous - Greasy

Streak:

white

Optical Properties of Ralstonite

Gladstone-Dale:

CI meas= 0.161 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= 0.19 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1629,KPDmeas= 0.1686,KC= 0.201

Optical Data:

Isotropic, n=1.43.

Calculated Properties of Ralstonite

Electron Density:

r_electron=2.52 gm/cc
note: r_Ralstonite=2.55 gm/cc.

Fermion Index

Fermion Index = 0.00644
Boson Index = 0.99356

Photoelectric:

PE_Ralstonite= 1.10 barns/electron
U=PE_Ralstonite x r_electron= 2.77 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Ralstonite is Not Radioactive

Ralstonite Classification

Dana Class:

11.6.12.1 (11)Halide Complexes; Alumino-fluorides

(11.6)with miscellaneous formulae

(11.6.12)Dana Group

11.6.12.1 Ralstonite NaxMgxAl2-x(F,OH)6·(H2O) F d3m 4/m 3 2/m

Strunz Class:

III/C.03-60 III - Halogenides

III/C - Double halogenides with water, Fluorides

III/C.03 - Prosopite - Boldyrevite series

III/C.03-10 Prosopite CaAL2(F,OH)8 A2/a 2/m

III/C.03-20 Chiolite Na5Al3F14 P 4/mnc 4/m 2/m 2/m

III/C.03-30 Weberite Na2MgAlF7 I mma 2/m 2/m 2/m

III/C.03-40 Usovite Ba2CaMgAl2F14 C 2/c or Cc Mono

III/C.03-45 Karasugite SrCaAl(F,OH)7 P 2₁/c 2/m

III/C.03-50 Carlhintzeite Ca2AlF7·(H2O) C1,C1 Tri

III/C.03-55 Rosenbergite AlF3·3(H2O) P 4/n 4/m

III/C.03-60 Ralstonite NaxMgxAl2-x(F,OH)6·(H2O) F d3m 4/m 3 2/m

III/C.03-70 Neighborite NaMgF3 Pcmn 2/m 2/m 2/m

III/C.03-80 Boldyrevite* NaCaMgAl3F14·4(H2O) None

Other Ralstonite Information

References:

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

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Ralstonite

NaxMgxAl2-x(F,OH)6·(H2O)
Dana No: 11.6.12.1 Strunz No: III/C.03-60
Locality:

Notes: