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Tarapacáite

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Tarapacá Region, Chile
© 2008, J. Weissman

Formula:
K
 
2
[CrO
 
4
]
System:OrthorhombicColour:Bright yellow, ...
Name:Named after its discovery locality, Tocopilla Pampa, Tarapacá, Chile.
Isostructural with:Mascagnite


Easily synthesised (compare lopezite).

Classification of Tarapacáite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:6/F.01-10
Nickel-Strunz 10th (pending) edition ID:7.FA.05

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
F : Chromates
A : Without additional anions
Dana 7th edition ID:35.1.1.1
Dana 8th edition ID:35.1.1.1

35 : ANHYDROUS CHROMATES
1 : A2XO4
Hey's CIM Ref.:27.2.1

27 : Sulphites, Chromates, Molybdates and Tungstates
2 : Chromates
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Type Occurrence of Tarapacáite

Type Locality:Oficina Maria Elena, Tocopilla Province, Antofagasta Region, Chile
Year of Discovery:1878
Associated Minerals at type locality:
LópeziteDietzeite

Physical Properties of Tarapacáite

Diaphaneity (Transparency):Transparent
Colour:Bright yellow, yellow-orange
Cleavage:Distinct/Good
On {001} and {010}, distinct.
Density (measured):2.74 g/cm3
Density (calculated):2.735 g/cm3
Comment:Measured value on artificial material.

Crystallography of Tarapacáite

Crystal System:Orthorhombic
Class (H-M):mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:a = 7.66Å, b = 10.39Å, c = 5.91Å
Ratio:a:b:c = 0.737 : 1 : 0.569
Unit Cell Volume:V 470.36 ų (Calculated from Unit Cell)
Morphology:Crystals thick tabular {001}.
Twinning:Twinning on {110} producing pseudo-hexagonal twins analogous to aragonite.

Optical Data of Tarapacáite

Type:Biaxial (-)
RI values: nα = 1.687 nβ = 1.722 nγ = 1.731
2V:Measured: 52° , Calculated: 52°
Maximum Birefringence:δ = 0.044

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:High
Dispersion:r > v weak

Chemical Properties of Tarapacáite

Formula:
K
 
2
[CrO
 
4
]
Essential elements:Cr, K, O
All elements listed in formula:Cr, K, O

Relationship of Tarapacáite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
7.FA.10Chromatite
Ca[CrO
 
4
]
7.FA.15Hashemite
Ba(Cr,S)O
 
4
7.FA.20Crocoite
Pb(CrO
 
4
)
Related Minerals - Hey's Index Grouping:

- +
27.2.2Lópezite
K
 
2
[Cr
 
2
O
 
7
]
27.2.3Chromatite
Ca[CrO
 
4
]
27.2.4Hashemite
Ba(Cr,S)O
 
4
27.2.5Crocoite
Pb(CrO
 
4
)
27.2.6Phoenicochroite
Pb
 
2
[O|CrO
 
4
]
27.2.7Santanaite
Pb
 
11
[O
 
12
|CrO
 
4
]
27.2.8Iranite
Pb
 
10
Cu[(F,OH)
 
2
|(CrO
 
4
)
 
6
|(SiO
 
4
)
 
2
]
27.2.9Hemihedrite
Pb
 
10
Zn[(F,OH)
 
2
|(CrO
 
4
)
 
6
|(SiO
 
4
)
 
2
]

Other Names for Tarapacáite

Other Languages:
German:Tarapacait
Russian:Тарапакаит
Spanish:Tarapacaita

Other Information

Other Information:Readily soluble in water.
Health Warning: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 Tarapacáite

Reference List:Raimondi, A. (1878) Minéraux du Pérou: Catalogue raisonné d’une collection des principaux types minéraux de la République. 336pp., Paris: 274.

Gossner (1904) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 39: 166.

Brendler (1923) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 58: 445 (quotes Mitscherlich (1830) Annalen der Physik, Halle, Leipzig: 18: 169).

Zachariasen and Ziegler (1931) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 80: 164.

Larsen, E.S. and Berman, H. (1934) The Microscopic Determination of the Nonopaque Minerals, Second edition, USGS Bulletin 848: 192.

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. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 644.

Acta Crystallographica (1972): B28: 2845.

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    Localities for Tarapacáite

    (TL) indicates type locality. ? 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
     
    • Antofagasta Region
      • Antofagasta Province
    		No reference listed
      • Tocopilla Province
    		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: 645; Acta Cryst. B28 (1972), 2843; J.W. Anthony, R.A. Bideaux, K.W. Bladh, M.C. Nichols: Handbook of Mineralogy, Vol. V (2003)
    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; Anthony, Bideaux, Bladh, Nichols (2003) Handbook of Mineralogy - Vol. 5.
    J.W. Anthony, R.A. Bideaux, K.W. Bladh, M.C. Nichols: Handbook of Mineralogy, Vol. V (2003)
    • Tarapacá Region
      • Iquique Province
    		J.W. Anthony, R.A. Bideaux, K.W. Bladh, M.C. Nichols: Handbook of Mineralogy, Vol. V (2003); American Mineralogist: 79: 1003-1008.
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