Lacroixite (original) (raw)

A valid IMA mineral species - grandfathered

About LacroixiteHide

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Colour:

Colourless, light yellow, light green, almost white; colourless in transmitted light.

Lustre:

Sub-Vitreous, Resinous, Dull

Specific Gravity:

3.126 - 3.29

Crystal System:

Monoclinic

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.

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 IdentifiersHide

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Long-form identifier:

mindat:1:1:2310:4

8e5f44b5-cf36-443e-92d1-0af05f14930e

IMA Classification of LacroixiteHide

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Approved, 'Grandfathered' (first described prior to 1959)

Type description reference:

Classification of LacroixiteHide

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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

41.5.5.1

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

Mineral SymbolsHide

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As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Physical Properties of LacroixiteHide

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Sub-Vitreous, Resinous, Dull

Colour:

Colourless, light yellow, light green, almost white; colourless in transmitted light.

Cleavage:

Poor/Indistinct
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 LacroixiteHide

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RI values:

_n_α = 1.546 _n_β = 1.563 _n_γ = 1.580

2V:

Measured: 89° , Calculated: 88°

δ = 0.034

Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.

Optical Extinction:

Inclined

Chemistry of LacroixiteHide

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Mindat Formula:

NaAl(PO4)F

Crystallography of LacroixiteHide

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Crystal System:

Monoclinic

Class (H-M):

2/m - Prismatic

Cell Parameters:

a = 6.414 Å, b = 8.207 Å, c = 6.885 Å
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 StructureHide

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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 DiffractionHide

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Powder Diffraction Data:

Geological EnvironmentHide

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Type Occurrence of LacroixiteHide

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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.

Geological Setting of Type Material:

Associated Minerals at Type Locality:

Reference:

Slavik, M.F. (1914) Sur les fluorophosphates ternaires de Al2O3, RO et R2O (morinite, ježekite, lacroixite). Bulletin de la Société Française de Minéralogie et de Cristallographie: 37: 152-162.

Other Language Names for LacroixiteHide

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Simplified Chinese:锥晶石

Traditional Chinese:錐晶石

Relationship of Lacroixite to other SpeciesHide

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Other Members of this group:

Common AssociatesHide

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Associated Minerals Based on Photo Data:

Related Minerals - Strunz-mindat GroupingHide

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Other InformationHide

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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 LacroixiteHide

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References for LacroixiteHide

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Reference List:

Palache, Charles, Berman, Harry, Frondel, Clifford (1951) The System of Mineralogy (7th ed.) Vol. 2 - Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Ect. John Wiley and Sons, New York.

Localities for LacroixiteHide

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This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

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- 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.