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Leucostaurite

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Formula:
Pb2B5O9Cl · 0.5H2O
System:
Orthorhombic
Colour:
White to colorless
Lustre:
Adamantine
Hardness:
4
Name:
is derived from the Greek “leukos” (white) and “stauros” (cross), and alludes to the white, cruciform twinned crystals

Classification of Leucostaurite

Approved
Approval Year:
2007
6.EA.05

6 : BORATES
E : Pentaborates
A : Neso-pentaborates

Physical Properties of Leucostaurite

Adamantine
Diaphaneity (Transparency):
Transparent
Colour:
White to colorless
Streak:
White
Hardness (Mohs):
4
Tenacity:
Brittle
Cleavage:
Perfect
perfect cleavage parallel to {010}, and a good cleavage parallel to {100}.
Density:
5.071 g/cm3 (Calculated)
Comment:
measured > 4.32

Optical Data of Leucostaurite

Type:
Biaxial
Dispersion:
strong, r > v
Pleochroism:
Non-pleochroic
Comments:
Mineral reacts with RI fluids. n > 1.790, Gladstone-Dale relationship, for the empirical formula is 1.849

Chemical Properties of Leucostaurite

IMA Formula:
Pb2B5O9Cl · 0.5H2O
Elements listed in formula:

Crystallography of Leucostaurite

Crystal System:
Orthorhombic
Class (H-M):
mm2 - Pyramidal
Space Group:
Pnn2
Cell Parameters:
a = 11.3757(20) Å, b = 11.5051(20) Å, c = 6.5568(7) Å
Ratio:
a:b:c = 0.989 : 1 : 0.57
Unit Cell Volume:
V 858.14 ų (Calculated from Unit Cell)
Z:
4
Twinning:
Many crystals show interpenetrated twinning [most probably either on (101) or (011)], forming a cruciform assemblage
X-Ray Powder Diffraction Data:
d-spacingIntensity
5.71 (80)
4.04 (100)
3.29 (40)
3.16 (30)
2.84 (100)
2.55 (40)
2.019 (70)
1.877 (40)

Type Occurrence of Leucostaurite

General Appearance of Type Material:
Leucostaurite forms thin colorless to white crystals tabular on {010} and striated //[100], sometimes grouped into sheaflike aggregates up to 0.8 mm in length
Place of Conservation of Type Material:
Musée géologique cantonal, Lausanne, Switzerland, under catalog number MGL 90000.
Geological Setting of Type Material:
interaction of evaporitic brines within the oxidation zone of a base-metal deposit

Relationship of Leucostaurite to other Species

Other Members of Group:
HilgarditeCa2B5O9Cl · H2O
KurgantaiteCaSr[B5O9]Cl · H2O
TyretskiteCa2B5O9OH · H2O
6.EA.05SborgiteNaB5O6(OH)4 · 3H2O
6.EA.10SantiteKB5O6(OH)4 · 2H2O
6.EA.10Ramanite-(Rb)RbB5O6(OH)4 · 2H2O
6.EA.10Ramanite-(Cs)CsB5O6(OH)4 · 2H2O
6.EA.15Ammonioborite(NH4)3B15O20(OH)8 · 4H2O
6.EA.25UlexiteNaCaB5O6(OH)6 · 5H2O

Other Names for Leucostaurite

Name in Other Languages:

Other Information

a weak, light-yellow fluorescence under short-wavelength UV light and no fluorescence under long-wavelength UV light.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Leucostaurite

Reference List:
Meisser, N. et al. (2010): The new microporous lead borate, leucostaurite, Pb2[B5O9]Cl · 0.5H2O, from Atacama Desert. 20th General Meeting of the IMA (IMA2010), Budapest, Hungary, August 21-27, CD of Abstracts, p. 485.

Brugger J, Meisser N, Ansermat S, Krivovichev S V, Kahlenberg V, Belton D, Ryan C G (2012) Leucostaurite, Pb2[B5O9]Cl·0.5H2O, from the Atacama Desert: The first Pb-dominant member of the hilgardite group, and micro-determination of boron minerals by PIGE. American Mineralogist 97, 1206-1212

Internet Links for Leucostaurite

mindat.org URL:
https://www.mindat.org/min-35579.html
Please feel free to link to this page.

Localities for Leucostaurite

(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Chile (TL)
 
  • Antofagasta Region
    • Antofagasta Province
      • Sierra Gorda District
        • Caracoles
Brugger J, Meisser N, Ansermat S, Krivovichev S V, Kahlenberg V, Belton D, Ryan C G (2012) Leucostaurite, Pb2[B5O9]Cl·0.5H2O, from the Atacama Desert: The first Pb-dominant member of the hilgardite group, and micro-determination of boron minerals by PIGE. American Mineralogist 97, 1206-1212
        • Caracoles mining district
          • Quebrada Honda
Brugger J, Meisser N, Ansermat S, Krivovichev S V, Kahlenberg V, Belton D, Ryan C G (2012) Leucostaurite, Pb2[B5O9]Cl·0.5H2O, from the Atacama Desert: The first Pb-dominant member of the hilgardite group, and micro-determination of boron minerals by PIGE. American Mineralogist 97, 1206-1212
Mineral and/or Locality  
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