Prosopite Mineral Data

Prosopite Mineral Data +

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General Prosopite Information

Chemical Formula:

CaAL2(F,OH)8

Composition:

Molecular Weight = 242.05 gm

Calcium 16.56 % Ca 23.17 % CaO

Aluminum 22.29 % Al 42.12 % Al₂O₃

Hydrogen 0.83 % H 7.44 % H₂O

Oxygen 13.22 % O

Fluorine 47.09 % F 47.09 % F

- % F -19.83 % -O=F₂

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

CaAl₂F₆(OH)₂

IMA Status:

Valid Species (Pre-IMA) 1853

Locality:

St. Peter's Dome near Pike's Peak, Colorado, USA. Link to MinDat.org Location Data.

Name Origin:

From the Greek prosopon - "mask."

Synonym:

ICSD 10267

PDF 5-307

Prosopite Image

Images:

Prosopite

Comments: Pale violet prosopite microcrystals.
Location: Ivigtut, Greenland. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Prosopite Crystallography

Axial Ratios:

a:b:c =0.6588:1:0.6021

Cell Dimensions:

a = 7.32, b = 11.11, c = 6.69, Z = 4; beta = 95° V = 542.00 Den(Calc)= 2.97

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): 4.35(1), 1.837(0.6), 2.13(0.6),

Forms:

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Forms: [ 0 1 0] [ 1 1 1] [ 1 1 1] [ 1 1 0]

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Crystal Structure:

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Pudovkina Z V , Chernitsova N M , Pyatenko Y A , Journal of Structural Chemistry , 14 (1973) p.345-347, Refinement of the crystalline structure of prosopite, CaAl2F4(OH)4

Physical Properties of Prosopite

Cleavage:

[111] Perfect, [111] Perfect, [111] Perfect

Color:

White, Greenish white, Reddish white.

Density:

2.88 - 2.89, Average = 2.88

Diaphaniety:

Transparent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Crystalline - Fine - Occurs as well-formed fine sized crystals.

Habit:

Massive - Granular - Common texture observed in granite and other igneous rock.

Hardness:

4-5 - Fluorite-Apatite

Luminescence:

None.

Luster:

Vitreous - Dull

Magnetism:

Nonmagnetic

Streak:

white

Optical Properties of Prosopite

Gladstone-Dale:

CI meas= 0.046 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.073 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1699,KPDmeas= 0.1749,KC= 0.1833

Optical Data:

Biaxial (+), a=1.501, b=1.503, g=1.51, bire=0.0090, 2V(Calc)=58, 2V(Meas)=62.75. Dispersion none.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Prosopite

Electron Density:

r_electron=2.81 gm/cc
note: r_Prosopite=2.89 gm/cc.

Fermion Index

Fermion Index = 0.00028
Boson Index = 0.99972

Photoelectric:

PE_Prosopite= 2.98 barns/electron
U=PE_Prosopite x r_electron= 8.39 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Prosopite is Not Radioactive

Prosopite Classification

Dana Class:

11.6.9.1 (11)Halide Complexes; Alumino-fluorides

(11.6)with miscellaneous formulae

(11.6.9)Dana Group

11.6.9.1 Prosopite CaAL2(F,OH)8 A2/a 2/m

Strunz Class:

III/C.03-10 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 Prosopite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

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Prosopite

CaAL2(F,OH)8
Dana No: 11.6.9.1 Strunz No: III/C.03-10
Locality:

Notes: