Montebrasite Mineral Data

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. Species and name natromontebrasite are discredited because natromontebrasite is a mixture of OH-rich amblygonite with lacro ixite and subordinate wardite

IMA Status:

Discredited IMA 2005 No. 05-E

Locality:

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

Name Origin:

Named for the locality in 1872.

Name Pronunciation:

Montebrasite + Pronunciation

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 Tanco Pegmatite, Bernic Lake, Manitoba at T = 295 K, Note: O3-x coordinate modified

View Additional jPOWD Structure files for Montebrasite
[10] [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

Diaphaneity:

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= 0.049 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.199,KPDmeas= 0.1999,KC= 0.2093
Ncalc = 1.63 - 1.64

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:

Bulk Density (Electron Density)=2.98 gm/cc
note: Specific Gravity of Montebrasite =3.03 gm/cc.

Fermion Index:

Fermion Index = 0.0038058115
Boson Index = 0.9961941885

Photoelectric:

PE_Montebrasite= 1.61 barns/electron
U=PE_Montebrasite x rElectron Density= 4.80 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Montebrasite is Not Radioactive

Montebrasite Classification

Dana Class:

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

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

(41.05.08)Amblygonite Group

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

41.05.08.02 Montebrasite? LiAl(PO4)(OH,F) P1 1

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

Strunz Class:

08.BB.05 08 - PHOSPHATES, ARSENATES, VANADATES

08.B - Phosphates, etc. with Additional Anions, without H2O

08.BB -With only medium-sized cations, (OH, etc.):RO4 £ 1:1

08.BB.05 Amblygonite (Li,Na)Al(PO4)(F,OH) P1 1

08.BB.05 Natromontebrasite? (Na,Li)Al(PO4)(OH,F) P1 1

08.BB.05 Montebrasite? LiAl(PO4)(OH,F) P1 1

08.BB.05 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)

See Also:

Links to other databases for Montebrasite :
1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - EUROmin Project
5 - Ecole des Mines de Paris
6 - GeoScienceWorld
7 - Google Images
8 - Google Scholar
9 - Handbook of Mineralogy (MinSocAm)
10 - Handbook of Mineralogy (UofA)
11 - MinDAT
12 - Mineralienatlas (Deutsch)
13 - Online Mineral Museum
14 - QUT Mineral Atlas
15 - Ruff.Info
16 - Scandinavian mineral gallery
17 - WWW-MINCRYST

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Ask about Montebrasite here :
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Print or Cut-and-Paste your Montebrasite Specimen Label here :

Montebrasite

LiAl(PO4)(OH,F)
Dana No: 41.05.08.02 Strunz No: 08.BB.05
Locality:

Notes: