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)

Environment:

Minor accessory mineral in nitrate deposits.

IMA Status:

Valid Species (Pre-IMA) 1878

Locality:

In Chile, in nitrate caliche deposits throughout the Atacama Desert. Link to MinDat.org Location Data.

Name Origin:

Named for its first noted occurrence in the Tocopilla Pampa, 170 km north of Antofagasta, Tarapaca, Chile.

Name Pronunciation:

Tarapacaite + Pronunciation

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:

Mouse
drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
Keyboard
S - Stereo Pair on/off
H - Help Screen
I - Data Info
A - Atoms On/Off
P - Polyhedra On/Off
B - Bonds On/Off
Help on Above

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

Diaphaneity:

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
Ncalc = 1.73

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:

Bulk Density (Electron Density)=2.65 gm/cc
note: Specific Gravity of Tarapacaite =2.74 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

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)
Concentration of Tarapacaite per GRapi unit =1,777.84 (PPM)

**Estimated Radioactivity from Tarapacaite** - mild
Specimen Size Weight/Volume (Sphere) *	Calculated Activity Becquerels (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:

35.01.01.01 (35)Anhydrous Chromates

(35.01)where (A+)2 XO4

(35.01.01)Dana Group

35.01.01.01 Tarapacaite K2CrO4 Pnam 2/m 2/m 2/m

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

References:

NAME( AntBidBlaNic4) 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 - 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

Search for Tarapacaite using:

[AOL] [Bing] [Dog Pile] [GeoScienceWorld] [HotBot] [Ixquick] [Lycos] [MAMMA] [Scirus] [Teoma] [WebCrawler] [Wikipedia] [YAHOO]

Visit our Advertisers for Tarapacaite :

A Bijoux Google Search for Tarapacaite
Adam's Minerals Google Search for Tarapacaite
Cape Minerals Google Search for Tarapacaite
Dakota Matrix Minerals Google Search for Tarapacaite
Excalibur Mineral Corp. Google Search for Tarapacaite
Exceptional Minerals Google Search for Tarapacaite
John Betts Fine Minerals Search for Tarapacaite
McDougall Minerals Google Search for Tarapacaite
Mineral News Website Link
Rock and Mineral Shows Google Search for Tarapacaite
Weinrich Minerals, Inc. Google Search for Tarapacaite

Ask about Tarapacaite here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

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

Tarapacaite

K2CrO4
Dana No: 35.01.01.01 Strunz No: 07.FA.05
Locality:

Notes: