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Lópezite

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Lópezite

Oficina Maria Elena, Tocopilla Province, Antofagasta, Chile
Lópezite

Huara, El Tamarugal Province, Tarapacá, Chile
Lópezite

Huara, El Tamarugal Province, Tarapacá, Chile
Lópezite

Oficina Maria Elena, Tocopilla Province, Antofagasta, Chile
Lópezite

Huara, El Tamarugal Province, Tarapacá, Chile
Lópezite

Huara, El Tamarugal Province, Tarapacá, Chile
Lópezite

Oficina Maria Elena, Tocopilla Province, Antofagasta, Chile
Lópezite

Huara, El Tamarugal Province, Tarapacá, Chile
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About LópeziteHide

Formula:
K2Cr2O7
Colour:
Orange-red, red
Lustre:
Vitreous
Hardness:
2½
Specific Gravity:
2.69
Crystal System:
Triclinic
Name:
For Emiliano López Saa (1871-1959), Chilean mining engineer and mineral collector associated with the Chilean nitrate mining industry.
Note: Most commercially available "lópezite" is, in fact, synthetic K2Cr2O7.


Classification of LópeziteHide

IMA status:
Approved, 'Grandfathered' (first described prior to 1959)
Strunz 8th ed.:
6/F.05-10
Nickel-Strunz 10th (pending) ed.:
7.FD.05

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
F : Chromates
D : Dichromates
Dana 7th ed.:
35.2.1.1
Dana 8th ed.:
35.2.1.1

35 : ANHYDROUS CHROMATES
2 : A2X2O7
Hey's CIM Ref.:
27.2.2

27 : Sulphites, Chromates, Molybdates and Tungstates
2 : Chromates

Physical Properties of LópeziteHide

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

Optical Data of LópeziteHide

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 LópeziteHide

Formula:
K2Cr2O7
Elements listed:
Cr, K, O - search for minerals with similar chemistry

Crystallography of LópeziteHide

Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 7.46 Å, b = 13.4 Å, c = 7.38 Å
α = 90.75°, β = 96.21°, γ = 97.96°
Ratio:
a:b:c = 0.557 : 1 : 0.551
Unit Cell 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 DiffractionHide

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)

Type Occurrence of LópeziteHide

Type Locality:
ⓘ Huara, El Tamarugal Province, Tarapacá, Chile
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
Geological Setting of Type Material:
nitrate rock
Associated Minerals at Type Locality:
UlexiteTarapacáiteDietzeite

Other Language Names for LópeziteHide

German:Lopezit
Spanish:Lopezita

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

27.2.1TarapacáiteK2(CrO4)Orth. mmm (2/m 2/m 2/m)
27.2.3ChromatiteCaCr6+O4Tet. 4/mmm (4/m 2/m 2/m) : I41/amd
27.2.4HashemiteBa(CrO4)Orth. mmm (2/m 2/m 2/m) : Pnma
27.2.5CrocoitePbCrO4Mon. 2/m : P21/b
27.2.6PhoenicochroitePb2(CrO4)OMon.
27.2.7SantanaitePb11(CrO4)O12Hex. 6 2 2 : P63 2 2
27.2.8IranitePb10Cu(CrO4)6(SiO4)2(OH)2Tric.
27.2.9HemihedritePb10Zn(CrO4)6(SiO4)2(OH)2Tric.

Other InformationHide

Notes:
Readily soluble in water.
Health Risks:
Chromate minerals contain the carcinogenic and mutagenic chromate ion. Always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest. Do not pour chromate-containing solutions down the drain.

References for LópeziteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Schabus (1850) Königliche Akademie der Wissenschaften, Vienna, Ber.: 5: 369 [artificial material].
Dufet (1890) Bulletin de la Société française de Minéralogie: 13: 346.
Groth, P. (1908) Chemische Krystallographie. Leipzig. 5 volumes: vol. 2: 586 [artificial material].
Gossner and Mussgnug (1930) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 72: 476 [artificial material].
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. & Brown, I. D. (1968): An accurate determination 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 LópeziteHide

Localities for LópeziteHide

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

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for 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 (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Canada
 
  • British Columbia
    • Nelson Mining Division
      • Trail
Uwe Kolitsch collection (anthropogenic?)
Chile
 
  • Antofagasta
    • 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
    • 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
    • Waterberg District
      • Naboomspruit (Mookgophong)
www.fc.up.pt/geo/ecrofi/377.PDF.; McDonald, I., Vaughan, D. J., & Tredoux, M. (1995). Platinum mineralization in quartz veins near Naboomspruit, central Transvaal. S. Afr. J. Geol, 98, 168-175.
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