Montebrasite Mineral Data

Montebrasite Mineral Data +

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General Montebrasite Information

Chemical Formula:

LiAl(PO4)(OH,F)

Composition:

Molecular Weight = 146.40 gm

Lithium 4.74 % Li 10.21 % Li₂O

Aluminum 18.43 % Al 34.82 % Al₂O₃

Phosphorus 21.16 % P 48.48 % P₂O₅

Hydrogen 0.52 % H 4.61 % H₂O

Oxygen 51.91 % O

Fluorine 3.24 % F 3.24 % F

- % F -1.37 % -O=F₂

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

LiAl(PO₄)(OH)_0.75F_0.25

Environment:

Forms large-sized crystals in lithium-bearing pegmatites.

IMA Status:

Valid Species (Pre-IMA) 1872

Locality:

Montebras, Creuse, France. Link to MinDat.org Location Data.

Name Origin:

Named for the locality.

Montebrasite Image

Images:

Montebrasite

Comments: Transparent, pale yellow, tabular crystals of Montebrasite on matrix.
Location: Newry, Oxford County, Maine, USA. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Montebrasite Crystallography

Axial Ratios:

a:b:c =0.7269:1:0.7093

Cell Dimensions:

a = 5.178, b = 7.123, c = 5.053, Z = 2; alpha = 112.03°, beta = 97.9°, gamma = 67.81° V = 158.45 Den(Calc)= 3.07

Crystal System:

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

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

By Intensity(I/I_o): 2.968(1), 3.164(0.9), 4.672(0.7),

Forms:

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Forms: [ 0 2 1] [ 0 1 0] [ 0 2 1] [ 1 1 0] [ 1 0 0] [ 0 0 1]

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Crystal Structure:

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Groat L A , Chakoumakos B C , Brouwer D H , Hoffman C M , Fyfe C A , Morell H , Schultz A J , American Mineralogist , 88 (2003) p.195-210, The amblygonite (LiAlPO4F) - montebrasite (LiAlPO4OH) solid solution:, A combined powder and single-crystal neutron diffraction and solid-state Li MAS, CP MAS,, and REDOR NMR study, Sample: from Dunton Gem Min, Oxford County, Maine at T = 295 K

View Additional jPOWD Structure files for Montebrasite
[11] [12] [13] [14] [15] [3] [4] [5] [6] [7] [8] [9]

Physical Properties of Montebrasite

Cleavage:

[100] Perfect, [110] Good, [011] Distinct

Color:

Bluish, Colorless, Greenish, Greenish gray, Gray white.

Density:

3.027

Diaphaniety:

Transparent to Translucent

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

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

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Hardness:

5.5-6 - Knife Blade-Orthoclase

Luster:

Vitreous - Greasy

Streak:

white

Optical Properties of Montebrasite

Gladstone-Dale:

CI meas= 0.045 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.059 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1971,KPDmeas= 0.1999,KC= 0.2093

Optical Data:

Biaxial (-), a=1.57-1.6, b=1.61, g=1.62, bire=0.0200-0.0500, 2V(Calc)=52-88, 2V(Meas)=81.5.

Calculated Properties of Montebrasite

Electron Density:

r_electron=2.98 gm/cc
note: r_Montebrasite=3.03 gm/cc.

Fermion Index

Fermion Index = 0.0038
Boson Index = 0.9962

Photoelectric:

PE_Montebrasite= 1.61 barns/electron
U=PE_Montebrasite x r_electron= 4.80 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Montebrasite is Not Radioactive

Montebrasite Classification

Dana Class:

41.5.8.2 (41)Anhydrous Phosphates, etc. Containing Hydroxyl or Halogen

(41.5)where (A B)2 (XO4) Zq

(41.5.8)Dana Group

41.5.8.1 Amblygonite (Li,Na)Al(PO4)(F,OH) P1 1

41.5.8.2 Montebrasite LiAl(PO4)(OH,F) P1 1

41.5.8.3 Natromontebrasite (Na,Li)Al(PO4)(OH,F) P1 1

Strunz Class:

VII/B.02-40 VII - Phosphates, Arsenates and Vanadates

VII/B - Waterfree phosphates with unfamiliar anions F, Cl, O,OH, cations of medium size: Mg, Mn, Fe, Cu, Zn, Pseudomalachite group and related compounds

VII/B.02 - Amblygonite group, Griphite - Tavorite

VII/B.02-10 Griphite Ca(Mn,Na,Li)6FeAl2(PO4)6(F,OH)2 P a3 2/m 3

VII/B.02-20 Tancoite HNa2LiAl(PO4)2(OH) Pbcb 2/m 2/m 2/m

VII/B.02-30 Amblygonite (Li,Na)Al(PO4)(F,OH) P1 1

VII/B.02-40 Montebrasite LiAl(PO4)(OH,F) P1 1

VII/B.02-50 Natromontebrasite (Na,Li)Al(PO4)(OH,F) P1 1

VII/B.02-60 Tavorite LiFe(PO4)(OH) P1 or P1 Tri

Other Montebrasite Information

References:

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

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Montebrasite

LiAl(PO4)(OH,F)
Dana No: 41.5.8.2 Strunz No: VII/B.02-40
Locality:

Notes: