Mineralogy Database

Tarapacaite Mineral Data

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General Tarapacaite Information

Help on Chemical  Formula: Chemical Formula: K2CrO4
Help on Composition: 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
Help on Empirical Formula: Empirical Formula: K2(CrO4)
Help on Environment: Environment: Minor accessory mineral in nitrate deposits.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1878
Help on Locality: Locality: In Chile, in nitrate caliche deposits throughout the Atacama Desert. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named for its first noted occurrence in the Tocopilla Pampa, 170 km north of Antofagasta, Tarapaca, Chile.
Help on Name Pronunciation: Name Pronunciation: Tarapacaite + Pronunciation Say TARAPACAITE
Help on Synonym: Synonym: ICSD 2402
  PDF 15-365

Tarapacaite Image

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

Tarapacaite Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =0.7374:1:0.5696
Help on Cell Dimensions: Cell Dimensions: a = 7.663, b = 10.391, c = 5.919, Z = 4; V = 471.31 Den(Calc)= 2.74
Help on Crystal System: Crystal System: Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: Pnam
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 3.078(1), 2.988(0.75), 2.96(0.4),

Physical Properties of Tarapacaite

Help on Cleavage: Cleavage: {001} Distinct, {010} Distinct
Help on Color: Color: Yellow, Light yellow.
Help on Density: Density: 2.74
Help on Diaphaneity: Diaphaneity: Transparent
Help on Luster: Luster: Vitreous (Glassy)
Help on Streak: Streak: light yellow

Optical Properties of Tarapacaite

Help on Gladstone-Dale: 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
Ncalc = 1.73
Help on Optical Data: 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

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=2.65 gm/cc
note: Specific Gravity of Tarapacaite =2.74 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.02
Boson Index = 0.98
Help on Photoelectric: Photoelectric: PETarapacaite = 10.15 barns/electron
U=PETarapacaite x relectron= 26.92 barns/cc.
Help on Radioactivity: Radioactivity:

GRapi = 562.48 (Gamma Ray American Petroleum Institute Units)
Concentration of Tarapacaite per GRapi unit =1,777.84 (PPM)

Estimated Radioactivity from Tarapacaite - mild
Curies (Ci)
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

Help on  Dana Class: Dana Class: (35)Anhydrous Chromates
  (35.01)where (A+)2 XO4
  (35.01.01)Dana Group Tarapacaite K2CrO4 Pnam 2/m 2/m 2/m
Help on  Strunz Class: Strunz Class: 07.FA.05 07 - SULFATES (SELENATES, TELLURATES)
  07.F - Chromates
  07.FA -Without additional anions
07.FA.05 Tarapacaite K2CrO4 Pnam 2/m 2/m 2/m

Other Tarapacaite Information

Help on References: References: NAME( AntBidBlaNic4) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)
Help on See Also: See Also: Links to other databases for Tarapacaite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Dana No: Strunz No: 07.FA.05





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