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Lópezite

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Formula:
K2[Cr2O7]
System:
Triclinic
Colour:
Orange-red, red
Lustre:
Vitreous
Hardness:
Name:
For Emiliano López Saa (1871-1959), Chilean mining engineer and mineral collector associated with the Chilean nitrate mining industry.
Note: Most commercially offered "lopezite" is in fact synthetic K2Cr2O7.

Classification of Lópezite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
7.FD.05

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
F : Chromates
D : Dichromates
Dana 7th ed.:
35.2.1.1
35.2.1.1

35 : ANHYDROUS CHROMATES
2 : A2X2O7
27.2.2

27 : Sulphites, Chromates, Molybdates and Tungstates
2 : Chromates
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http://www.mindat.org/min-2433.html
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Type Occurrence of Lópezite

General Appearance of Type Material:
ball-like aggregates, to 1 mm.
Place of Conservation of Type Material:
National Museum of Natural History, Washington, DC, USA C5487
Year of Discovery:
1937
Geological Setting of Type Material:
nitrate rock
Associated Minerals at Type Locality:

Physical Properties of Lópezite

Vitreous
Diaphaneity (Transparency):
Transparent
Colour:
Orange-red, red
Streak:
light yellow
Hardness (Mohs):
Cleavage:
Perfect
[010] perfect, [100] distinct, [001] distinct
Density:
2.69 g/cm3 (Measured)    2.704 g/cm3 (Calculated)

Crystallography of Lópezite

Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 7.46Å, b = 13.4Å, c = 7.38Å
α = 90.75°, β = 96.21°, γ = 97.96°
Ratio:
a:b:c = 0.557 : 1 : 0.551
Unit Cell Volume:
V 722.41 ų
Z:
4
Morphology:
Ball-like aggregates (~ 1 mm diameter). Artificial crystals are short prismatic [001].
Twinning:
Observed on artificial crystals.
X-Ray Powder Diffraction Data:
d-spacingIntensity
4.87 (45)
3.658 (85)
3.472 (80)
3.298 (100)
3.063 (30)
3.027 (30)
2.877 (30)
Comments:
synthetic (ICDD 27-0380)

Optical Data of Lópezite

Type:
Biaxial (+)
RI values:
nα = 1.714 nβ = 1.732 nγ = 1.805
2V:
Measured: 50° , Calculated: 56°
Max Birefringence:
δ = 0.091
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
r > v, medium
Pleochroism:
Visible
Comments:
X = reddish yellow
Y = yellow
Z = greenish yellow

Chemical Properties of Lópezite

Formula:
K2[Cr2O7]
Essential elements:
All elements listed in formula:
Empirical Formula:
K2[Cr26+O7]

Relationship of Lópezite to other Species

27.2.1TarapacáiteK2[CrO4]
27.2.3ChromatiteCa[CrO4]
27.2.4HashemiteBa(Cr,S)O4
27.2.5CrocoitePb(CrO4)
27.2.6PhoenicochroitePb2(CrO4)O
27.2.7SantanaitePb11(CrO4)O12
27.2.8IranitePb10Cu(CrO4)6(SiO4)2(OH)2
27.2.9HemihedritePb10Zn(CrO4)6(SiO4)2(F,OH)2

Other Names for Lópezite

Name in Other Languages:
German:Lopezit
Spanish:Lopezita

Other Information

Other Information:
Readily soluble in water.
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 Lópezite

Reference List:
Schabus (1850) Konigliche Akademie der Wissenschaften, Vienna, Ber.: 5: 369 (artif. mat.).

Dufet (1890) Bulletin de la Société française de Minéralogie: 13: 346.

Groth, P. (1908) Chemische Krystallographie. Leipzig. 5 volumes: vol. 2: 586 (artif. mat.).

Gossner and Mussgnug (1930) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 72: 476 (artif. mat.).

Bandy (1937) American Mineralogist: 22: 929-930.

Mémoires du Bureau de Recherches Géologiques et Minières: 8: 271-274.

Palache, Charles, Harry Berman & Clifford Frondel (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Seventh edition, Volume II: 645-646.

Brandon, J. K. & I.D. Brown (1968): "An accurate deermination of the crystal structure of triclinic potassium dichromate" Canadian Journal of Chemistry: 46: 933-941.

Brunton, G. (1983): "Refinement of the structure of K2Cr2O7": Mat. Res. Bull. 8, 271-274.

Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (2003) Handbook of Mineralogy, Volume V. Borates, Carbonates, Sulfates. Mineral Data Publishing, Tucson, AZ, 813pp.: 411.

Internet Links for Lópezite

Localities for Lópezite

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.
(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.
Canada
 
  • British Columbia
    • Nelson Mining Division
      • Trail
Uwe Kolitsch collection (anthropogenic?)
Chile
 
  • Antofagasta Region
    • Tocopilla Province
      • Oficina Maria Elena
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 646; O'Donoghue (1978) "Encyclopedia of Minerals & Gemstones", p283.
  • Tarapacá Region
    • El Tamarugal Province
Bandy (1937) American Mineralogist: 22: 929-930.
Handbook of Mineralogy - Anthony, Bideaux, Bladh, Nichols; American Mineralogist: 79: 1003-1008.
South Africa
 
  • Limpopo Province
    • Bushveld Complex
www.fc.up.pt/geo/ecrofi/377.PDF.
Mineral and/or Locality  
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