Lacroixite Mineral Data

Lacroixite Mineral Data +

General Lacroixite Information

Chemical Formula:

NaAl(PO4)F

Composition:

Molecular Weight = 163.94 gm

Sodium 14.02 % Na 18.90 % Na₂O

Aluminum 16.46 % Al 31.10 % Al₂O₃

Phosphorus 18.89 % P 43.29 % P₂O₅

Oxygen 39.04 % O

Fluorine 11.59 % F 11.59 % F

- % F -4.88 % -O=F₂

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

NaAl(PO₄)F

IMA Status:

Valid Species (Pre-IMA) 1914

Locality:

Link to MinDat.org Location Data.

Synonym:

ICSD 40522

PDF 39-325

Lacroixite Image

Images:

Lacroixite Berlinite

Comments: Pale olive green crystalline lacroixite with white crystalline berlinite.
Location: Rusororo Pegmatite, Gatumba, Gisenyi, Rwanda. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Lacroixite Crystallography

Axial Ratios:

a:b:c =0.7815:1:0.8389

Cell Dimensions:

a = 6.414, b = 8.207, c = 6.885, Z = 4; beta = 115.47° V = 327.20 Den(Calc)= 3.33

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/c

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

By Intensity(I/I_o): 2.9(1), 2.47(0.85), 3.159(0.71),

Crystal Structure:

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Lahti S I , Pajunen A , American Mineralogist , 70 (1985) p.849-855, New data on lacroixite, NaAlFPO4

Physical Properties of Lacroixite

Cleavage:

[111] Indistinct, [111] Indistinct

Color:

Colorless, Gray, Gray white, Light green, Light yellow.

Density:

3.29

Hardness:

4.5 - Between Fluorite and Apatite

Luster:

Vitreous - Resinous

Streak:

white

Optical Properties of Lacroixite

Gladstone-Dale:

CI meas= 0.075 (Fair) - where the CI = (1-KPDmeas/KC)
CI calc= 0.086 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1691,KPDmeas= 0.1711,KC= 0.185

Optical Data:

Biaxial (-), a=1.546, b=1.563, g=1.58, bire=0.0340, 2V(Calc)=88, 2V(Meas)=89.

Calculated Properties of Lacroixite

Electron Density:

r_electron=3.21 gm/cc
note: r_Lacroixite=3.29 gm/cc.

Fermion Index

Fermion Index = 0.00018
Boson Index = 0.99982

Photoelectric:

PE_Lacroixite= 1.67 barns/electron
U=PE_Lacroixite x r_electron= 5.35 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Lacroixite is Not Radioactive

Lacroixite Classification

Dana Class:

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

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

(41.5.5)Dana Group

41.5.5.1 Lacroixite NaAl(PO4)F C 2/c 2/m

41.5.5.2 Durangite NaAl(AsO4)F C 2/c 2/m

41.5.5.3 Maxwellite NaFe(AsO4)F Aa,A2/a Mono

Strunz Class:

VII/B.25-40 VII - Phosphates, Arsenates and Vanadates

VII/B - Waterfree phosphates with unfamiliar anions F, Cl, O, OH. cations of medium and big size: Mg, Cu, Zn, and Ca, Na, K, Ba, Pb

VII/B.25 - Isokite - Thadeuite series

VII/B.25-10 Isokite CaMg(PO4)F C 2/c 2/m

VII/B.25-20 Panasqueiraite CaMg(PO4)(OH,F) C 2/c 2/m

VII/B.25-30 Tilasite CaMg(AsO4)F C 2/c 2/m

VII/B.25-40 Lacroixite NaAl(PO4)F C 2/c 2/m

VII/B.25-50 Durangite NaAl(AsO4)F C 2/c 2/m

VII/B.25-55 Maxwellite NaFe(AsO4)F Aa,A2/a Mono

VII/B.25-60 Nacaphite Na(Na,Ca)2(PO4)F P1 1

VII/B.25-70 Spodiosite? Ca2(PO4)F Pbcm 2/m 2/m 2/m

VII/B.25-80 Thadeuite (Ca,Mn)(Mg,Fe,Mn)3(PO4)2(OH,F)2 C 222₁ 2 2 2

Other Lacroixite Information

References:

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

See Also:

Links to other databases for Lacroixite :
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 - WWW-MINCRYST 13 -École des Mines de Paris

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Lacroixite

NaAl(PO4)F
Dana No: 41.5.5.1 Strunz No: VII/B.25-40
Locality:

Notes: