Lacroixite
A valid IMA mineral species - grandfathered
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About Lacroixite
Alfred Lacroix at his desk
Formula:
NaAl(PO4)F
Colour:
Colourless, light yellow, light green, almost white; colourless in transmitted light.
Lustre:
Sub-Vitreous, Resinous, Dull
Hardness:
4½
Specific Gravity:
3.126 - 3.29
Crystal System:
Monoclinic
Member of:
Name:
Named in 1914 by František Slavik in honor of Antoine François Alfred Lacroix [February 4, 1863, Macon, Saône-et-Loire, France - March 12, 1948, Paris, France], a famous French mineralogist.
Dimorph of:
Frequently occurs as grains and rods in the altered margins of blocky crystals and grains of amblygonite or montebrasite embedded in granite pegmatite matrix. Not usually found in montebrasite crystals extending into cavities. Pure grains of lacroixite are uncommon.
Unique Identifiers
Mindat ID:
2310
Long-form identifier:
mindat:1:1:2310:4
IMA Classification of Lacroixite
Approved, 'Grandfathered' (first described prior to 1959)
First published:
1914
Classification of Lacroixite
8.BH.10
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
H : With medium-sized and large cations, (OH,etc.):RO4 = 1:1
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
H : With medium-sized and large cations, (OH,etc.):RO4 = 1:1
41.5.5.1
41 : ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
5 : (AB)2(XO4)Zq
41 : ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
5 : (AB)2(XO4)Zq
22.1.2
22 : Phosphates, Arsenates or Vanadates with other Anions
1 : Phosphates, arsenates or vanadates with fluoride
22 : Phosphates, Arsenates or Vanadates with other Anions
1 : Phosphates, arsenates or vanadates with fluoride
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference |
|---|---|---|
| Lac | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Lacroixite
Sub-Vitreous, Resinous, Dull
Transparency:
Translucent
Colour:
Colourless, light yellow, light green, almost white; colourless in transmitted light.
Streak:
White
Hardness:
4½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Poor/Indistinct
Parallel to (111) and 111) only.
Parallel to (111) and 111) only.
Fracture:
Irregular/Uneven
Density:
3.126 - 3.29 g/cm3 (Measured) 3.29 g/cm3 (Calculated)
Optical Data of Lacroixite
Type:
Biaxial (-)
RI values:
nα = 1.546 nβ = 1.563 nγ = 1.580
2V:
Measured: 89° , Calculated: 88°
Birefringence:
0.034
Max. Birefringence:
δ = 0.034
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars.
Surface Relief:
Moderate
Dispersion:
Slight r
Optical Extinction:
Inclined
Chemistry of Lacroixite
Mindat Formula:
NaAl(PO4)F
Element Weights:
Crystallography of Lacroixite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Setting:
C2/c
Cell Parameters:
a = 6.414 Å, b = 8.207 Å, c = 6.885 Å
β = 115.47°
β = 115.47°
Ratio:
a:b:c = 0.782 : 1 : 0.839
Unit Cell V:
327.20 ų (Calculated from Unit Cell)
Morphology:
Usually massive or intergrown with other minerals. Rarely observed as fragmentary crystals.
Comment:
Pseudo-orthorhombic
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0000996 | Lacroixite | Lahti S I, Pajunen A (1985) New data on lacroixite, NaAlFPO4 American Mineralogist 70 849-855 |  | 1985 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.73 Å | (51) |
| 4.627 Å | (32) |
| 3.155 Å | (100) |
| 2.895 Å | (98) |
| 2.476 Å | (57) |
| 2.166 Å | (43) |
| 1.578 Å | (27) |
Comments:
ICDD 39-325
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 34 : Complex granite pegmatites | |
| 36 : Carbonatites, kimberlites, and related igneous rocks |
Type Occurrence of Lacroixite
General Appearance of Type Material:
intergrowths, alteration rims, druses
Place of Conservation of Type Material:
Charles University, Prague, Czech Republic, 7400;
Harvard University, Cambridge, Massachusetts, USA, 86746.
Harvard University, Cambridge, Massachusetts, USA, 86746.
Geological Setting of Type Material:
Granite pegmatites
Associated Minerals at Type Locality:
Other Language Names for Lacroixite
Dutch:Lacroixiet
German:Lacroixit
Russian:Лакруаит
Simplified Chinese:锥晶石
Spanish:Lacroixita
Traditional Chinese:錐晶石
Relationship of Lacroixite to other Species
Member of:
Other Members of Tilasite Group:
| Arsenatrotitanite | NaTi(AsO4)O | Mon. 2/m : B2/b |
| Durangite | NaAl(AsO4)F | Mon. 2/m : B2/b |
| Isokite | CaMg(PO4)F | Mon. 2/m : B2/b |
| Kononovite | NaMg(SO4)F | Mon. 2/m : B2/b |
| Maxwellite | NaFe3+(AsO4)F | Mon. 2/m : P2/m |
| Panasqueiraite | CaMg(PO4)(OH) | Mon. |
| Reznitskyite | CaMg(VO4)F | Mon. 2/m : B2/b |
| Tilasite | CaMg(AsO4)F | Mon. |
Common Associates
Associated Minerals Based on Photo Data:
| 2 photos of Lacroixite associated with Amblygonite | LiAl(PO4)F |
| 1 photo of Lacroixite associated with Berlinite | AlPO4 |
| 1 photo of Lacroixite associated with Montebrasite | LiAl(PO4)(OH) |
| 1 photo of Lacroixite associated with Scorzalite | Fe2+Al2(PO4)2(OH)2 |
| 1 photo of Lacroixite associated with Apatite | Ca5(PO4)3(Cl/F/OH) |
| 1 photo of Lacroixite associated with Wodginite | Mn2+Sn4+Ta2O8 |
Related Minerals - Strunz-mindat Grouping
| 8.BH. | Peterchinite | Zn3Zn2(OH)6As[O3(OH)3] |
| 8.BH. | Reznitskyite | CaMg(VO4)F |
| 8.BH. | Cuprozheshengite | Pb4CuZn2(AsO4)2(PO4)2(OH)2 |
| 8.BH. | Zheshengite | Pb4ZnZn2(AsO4)2(PO4)2(OH)2 |
| 8.BH. | Crimsonite | PbFe3+2(PO4)2(OH)2 |
| 8.BH.05 | Thadeuite | Ca(Mg,Fe2+)3(PO4)2(OH,F)2 |
| 8.BH.10 | Panasqueiraite | CaMg(PO4)(OH) |
| 8.BH.10 | Isokite | CaMg(PO4)F |
| 8.BH.10 | Arsenatrotitanite | NaTi(AsO4)O |
| 8.BH.10 | Maxwellite | NaFe3+(AsO4)F |
| 8.BH.10 | Durangite | NaAl(AsO4)F |
| 8.BH.10 | Kononovite | NaMg(SO4)F |
| 8.BH.15 | Drugmanite | Pb2Fe3+(PO4)(PO3OH)(OH)2 |
| 8.BH.20 | Nigelcookite | PbFe2+2V3+2(PO4)3(OH)3 |
| 8.BH.20 | Plumbojohntomaite | PbFe2+2Fe3+2(PO4)3(OH)3 |
| 8.BH.20 | Cirrolite | Ca3Al2(PO4)3(OH)3 (?) |
| 8.BH.20 | Penikisite | Ba(Mg,Fe2+,Ca)2Al2(PO4)3(OH)3 |
| 8.BH.20 | Perloffite | Ba(Mn2+,Fe2+)2Fe3+2(PO4)3(OH)3 |
| 8.BH.20 | Bjarebyite Group | |
| 8.BH.20 | Strontioperloffite | SrMn2+2Fe3+2(PO4)3(OH)3 |
| 8.BH.20 | Plumboperloffite | PbMn2+2Fe3+2(PO4)3(OH)3 |
| 8.BH.20 | Johntomaite | BaFe2+2Fe3+2(PO4)3(OH)3 |
| 8.BH.20 | Bjarebyite | (Ba,Sr)(Mn2+,Fe2+,Mg)2Al2(PO4)3(OH)3 |
| 8.BH.20 | Kulanite | Ba(Fe2+,Mn2+,Mg)2(Al,Fe3+)2(PO4)3(OH)3 |
| 8.BH.25 | Bertossaite | Li2CaAl4(PO4)4(OH)4 |
| 8.BH.25 | Natropalermoite | Na2SrAl4(PO4)4(OH)4 |
| 8.BH.25 | Palermoite | Li2SrAl4(PO4)4(OH)4 |
| 8.BH.30 | Sewardite | CaFe3+2(AsO4)2(OH)2 |
| 8.BH.30 | Carminite | PbFe3+2(AsO4)2(OH)2 |
| 8.BH.35 | Adelite | CaMg(AsO4)(OH) |
| 8.BH.35 | Duftite | PbCu(AsO4)(OH) |
| 8.BH.35 | Cobaltaustinite | CaCo(AsO4)(OH) |
| 8.BH.35 | Nickelaustinite | CaNi(AsO4)(OH) |
| 8.BH.35 | Gabrielsonite | PbFe3+(As3+O3)O |
| 8.BH.35 | Conichalcite | CaCu(AsO4)(OH) |
| 8.BH.35 | Arsendescloizite | PbZn(AsO4)(OH) |
| 8.BH.35 | Duftite-alpha | PbCu(AsO4)(OH) |
| 8.BH.35 | Gottlobite | CaMg(VO4)(OH) |
| 8.BH.35 | Austinite | CaZn(AsO4)(OH) |
| 8.BH.35 | Hermannroseite | CaCu(PO4)(OH) |
| 8.BH.35 | Tangeite | CaCu(VO4)(OH) |
| 8.BH.40 | Čechite | PbFe2+(VO4)(OH) |
| 8.BH.40 | Khorixasite | (Bi0.67◻0.33)Cu(VO4)(OH) |
| 8.BH.40 | Mottramite | PbCu(VO4)(OH) |
| 8.BH.40 | Descloizite | PbZn(VO4)(OH) |
| 8.BH.40 | Pyrobelonite | PbMn2+(VO4)(OH) |
| 8.BH.45 | Bayldonite | PbCu3(AsO4)2(OH)2 |
| 8.BH.45 | Vésigniéite | BaCu3(VO4)2(OH)2 |
| 8.BH.50 | Paganoite | NiBi(AsO4)O |
| 8.BH.55 | Jagowerite | BaAl2(PO4)2(OH)2 |
| 8.BH.55 | Harrisonite | Ca(Fe2+,Mg)6(PO4)2(SiO4)2 |
| 8.BH.60 | Attakolite | CaMn2+Al4(SiO3OH)(PO4)3(OH)4 |
| 8.BH.65 | Leningradite | PbCu3(VO4)2Cl |
| 8.BH.70 | Katiarsite | KTiO(AsO4) |
| 8.BH.70 | Yurgensonite | K2SnTiO2(AsO4)2 |
| 8.BH.75 | Melanarsite | K3Cu7Fe3+O4(AsO4)4 |
| 8.BH.80 | Evseevite | Na2Mg(AsO4)F |
| 8.BH.80 | Moraskoite | Na2Mg(PO4)F |
| 8.BH.85 | Piccoliite | NaCaMn3+2(AsO4)2O(OH) |
Other Information
Notes:
Readily soluble in HCl and H2SO4.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Lacroixite
mindat.org URL:
https://www.mindat.org/min-2310.html
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References for Lacroixite
Localities for Lacroixite
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The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
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Rožná Hradisko, Rožná pegmatite, Rožná, Žďár nad Sázavou District, Vysočina Region, Czech Republic