Tarapacaite Mineral Data

Tarapacaite Mineral Data +

General Tarapacaite Information

Chemical Formula:

K2CrO4

Composition:

Molecular Weight = 194.19 gm

Potassium 40.27 % K 48.51 % K₂O

Chromium 26.78 % Cr 51.49 % CrO₃

Oxygen 32.96 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

K₂(CrO₄)

IMA Status:

Valid Species (Pre-IMA) 1878

Locality:

Link to MinDat.org Location Data.

Synonym:

ICSD 2402

PDF 15-365

Tarapacaite Image

Images:

Tarapacaite

Comments: Pale brown translucent tarapacaite, deliquescent granular.
Location: Tarapaca, Chile. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Tarapacaite Crystallography

Axial Ratios:

a:b:c =0.7374:1:0.5696

Cell Dimensions:

a = 7.663, b = 10.391, c = 5.919, Z = 4; V = 471.31 Den(Calc)= 2.74

Crystal System:

Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: Pnam

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.078(1), 2.988(0.75), 2.96(0.4),

Crystal Structure:

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McGinnety J A , Acta Crystallographica, Section B , 28 (1972) p.2845-2852, Redetermination of the structures of potassium sulphate and potassium chromate:, the effect of electrostatic crystal forces upon observed bond length

Physical Properties of Tarapacaite

Cleavage:

[001] Distinct, [010] Distinct

Color:

Yellow, Light yellow.

Density:

2.74

Diaphaniety:

Transparent

Luster:

Vitreous (Glassy)

Streak:

light yellow

Optical Properties of Tarapacaite

Gladstone-Dale:

CI meas= 0.027 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.027 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2603,KPDmeas= 0.2603,KC= 0.2676

Optical Data:

Biaxial (-), a=1.687, b=1.722, g=1.731, bire=0.0440, 2V(Calc)=52, 2V(Meas)=52.

Calculated Properties of Tarapacaite

Electron Density:

r_electron=2.65 gm/cc
note: r_Tarapacaite=2.74 gm/cc.

Fermion Index

Fermion Index = 0.02564
Boson Index = 0.97436

Photoelectric:

PE_Tarapacaite= 10.15 barns/electron
U=PE_Tarapacaite x r_electron= 26.92 barns/cc.

Radioactivity:

GRapi = 562.48 (Gamma Ray American Petroleum Institute Units)

**Estimated Radioactivity from Tarapacaite** - mild
Specimen Size Weight/Volume (Sphere) *	Calculated Activity Bequerols (Bq)	Calculated Activity Curies (Ci)	Estimated Activity GR(api)	Estimated Exposure (mRem**)/hr If Held in Hand For One Hour
1000 gm / 8.87 cm	12,201	3.30E-07	562.48	0.18
100 gm / 4.12 cm	1,220	3.30E-08	56.25	0.02
10 gm / 1.91 cm	122	3.30E-09	5.62	0.00
1 gm / 8.87 mm	12	3.30E-10	0.56	0.00
0.1 gm / 4.12 mm	1	3.30E-11	0.06	0.00
0.01 gm / 1.91 mm	0	3.30E-12	0.01	0.00
0.001 gm / 0.89 mm	0	3.30E-13	0.00	0.00

Weight of pure Tarapacaite in grams (gm) and Calculated Diameter of a Sphere with a Density of 2.74 gm/cc.*
Goverment Estimate of Average Annual Exposure ( 360 mRem) **
Note: 10 microsieverts/hr = 1 mRem/hr **
Max Permissable Adult Dose 50,000 mRem/yr (hands), 15,000 mRem/yr (eyes)
Lethal Dose LD(50) Exposure 400,000 to 500,000 mRem

Tarapacaite Classification

Dana Class:

35.1.1.1 (35)Anhydrous Chromates

(35.1)where (A+)2 XO4

(35.1.1)Dana Group

35.1.1.1 Tarapacaite K2CrO4 Pnam 2/m 2/m 2/m

Strunz Class:

VI/F.01-10 VI - Sulfates,Chromates,Molybdates and Tungstates

VI/F - Chromates [CrO4]2-

VI/F.01 - Tarapacaite - Crocoite series

VI/F.01-10 Tarapacaite K2CrO4 Pnam 2/m 2/m 2/m

VI/F.01-20 Chromatite CaCrO4 I 4₁/amd 4/m 2/m 2/m

VI/F.01-30 Crocoite PbCrO4 P 2₁/n 2/m

Other Tarapacaite Information

References:

PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Tarapacaite :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 - EUROmin Project 4 -Google Images 5 -Google Scholar 6 -Handbook of Mineralogy (UofA) 7 -MinDAT 8 -MinMax(Deutsch) 9 -MinMax(English) 10 -Mineralienatlas (Deutsch) 11 -QUT Mineral Atlas 12 -École des Mines de Paris

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Print or Cut-and-Paste your Tarapacaite Specimen Label here :

Tarapacaite

K2CrO4
Dana No: 35.1.1.1 Strunz No: VI/F.01-10
Locality:

Notes: