Lopezite Mineral Data

General Lopezite Information

Chemical Formula:

K2Cr2O7

Composition:

Molecular Weight = 294.18 gm

Potassium 26.58 % K 32.02 % K₂O

Chromium 35.35 % Cr 67.98 % CrO₃

Oxygen 38.07 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

K₂Cr₂O₇

Environment:

Rare secondary mineral in vugs in massive nitrate rock.

IMA Status:

Valid Species (Pre-IMA) 1937

Locality:

In Chile, in Tarapaca, from Oficina Rosario, Huara, Pampa del Iquique; Oficina Maria Elena, near Tocopilla, Pampa del Tocopilla; and at Zapiga. Link to MinDat.org Location Data.

Name Origin:

Named for Emiliano Lopez Saa (1871-1959), Iquique, Chile, Chilean mining engineer and mineral collector long associated with the Chilean nitrate industry.

Name Pronunciation:

Lopezite

Synonym:

ICSD 10371

PDF 27-380

Lopezite Image

Images:

Lopezite

Comments: yellowish granular lopezite.
Location: Tarapaca, Chile. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Lopezite Crystallography

Axial Ratios:

a:b:c =0.5597:1:0.5507

Cell Dimensions:

a = 7.5, b = 13.4, c = 7.38, Z = 4; alpha = 98°, beta = 90.85°, gamma = 96.217° V = 730.07 Den(Calc)= 2.68

Crystal System:

Triclinic - PinacoidalH-M Symbol ( 1) Space Group: P1

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

By Intensity(I/I_o): 3.32(1), 3.49(0.3), 3.68(0.2),

Crystal Structure:

Mouse
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drag2 - RMB Resize/Rotate
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Weakley T J R , Ylvisaker E R , Yager R J , Stephens J E , Wiegel R D , Mengis M , Wu P , Photinos P , Abrahams S C , Acta Crystallographica, Section B , 60 (2004) p.705-715, Phase transitions in K2Cr3O7 and structural redetermination of phase II, Locality: synthetic, Sample: Crystal 2

Physical Properties of Lopezite

Cleavage:

{010} Perfect, {100} Distinct, {001} Distinct

Color:

Orange red, Red.

Density:

2.69

Diaphaneity:

Transparent

Hardness:

2.5 - Finger Nail

Luster:

Vitreous (Glassy)

Streak:

light yellow

Optical Properties of Lopezite

Gladstone-Dale:

CI meas= 0.04 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.036 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.28,KPDmeas= 0.2789,KC= 0.2905
Ncalc = 1.78

Optical Data:

Biaxial (+), a=1.714, b=1.732, g=1.805, bire=0.0910, 2V(Calc)=56, 2V(Meas)=50.

Calculated Properties of Lopezite

Electron Density:

Bulk Density (Electron Density)=2.59 gm/cc
note: Specific Gravity of Lopezite =2.68 gm/cc.

Fermion Index:

Fermion Index = 0.03
Boson Index = 0.97

Photoelectric:

PE_Lopezite= 10.72 barns/electron
U=PE_Lopezite x r_electron= 27.75 barns/cc.

Radioactivity:

GRapi = 370.25 (Gamma Ray American Petroleum Institute Units)
Concentration of Lopezite per GRapi unit = 0.27 (%)

Estimated Radioactivity from Lopezite - barely detectable

Lopezite Classification

Dana Class:

35.02.01.01 (35)Anhydrous Chromates

(35.02)where (A+)2 X2O7

(35.02.01)Dana Group

35.02.01.01 Lopezite K2Cr2O7 P1 1

Strunz Class:

07.FD.05 07 - SULFATES (SELENATES, TELLURATES)

07.F - Chromates

07.FD -Dichromates

07.FD.05 Lopezite K2Cr2O7 P1 1

Other Lopezite 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 Lopezite :
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
15 - WWW-MINCRYST

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Ask about Lopezite 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 Lopezite Specimen Label here :

Lopezite

K2Cr2O7
Dana No: 35.02.01.01 Strunz No: 07.FD.05
Locality:

Notes: