Fornacite Mineral Data

General Fornacite Information

Chemical Formula:

Pb2Cu(CrO4)(AsO4)(OH)

Composition:

Molecular Weight = 749.87 gm

Chromium 6.93 % Cr 13.33 % CrO₃

Copper 8.47 % Cu 9.54 % Cu₂O

Arsenic 9.99 % As 15.33 % As₂O₅

Hydrogen 0.13 % H 1.20 % H₂O

Lead 55.26 % Pb 59.53 % PbO

Oxygen 19.20 % O

______ ______

100.00 % 98.93 % = TOTAL OXIDE

Empirical Formula:

Pb₂Cu(AsO₄)(CrO₄)(OH)

Environment:

Oxidized zones of some hydrothermal base-metal deposits.

IMA Status:

Valid Species (Pre-IMA) 1915

Locality:

Djoue and Reneville, Congo Republic. Link to MinDat.org Location Data.

Name Origin:

Named for Lucien Lewis Forneau (1867-1930), Colonial Governor of the French Congo.

Name Pronunciation:

Fornacite + Pronunciation

Synonym:

ICSD 26828

PDF 15-200

Fornacite Image

Images:

Fornacite

Comments: Dark, prismatic crystals of fornacite on matrix.
Location: El Khun mine, Anarak, Iran. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Images:

Fornacite

Comments: Emerald green platy crystals to 0.75mm on a pink to white, siliceous matrix.
Location: Lone Star mine, Copperopolis, Yavapai County, Arizona. Scale: Picture size 1.4 cm.
© Tom Loomis / Dakota Matrix

Fornacite Crystallography

Axial Ratios:

a:b:c =1.3384:1:2.9543

Cell Dimensions:

a = 7.91, b = 5.91, c = 17.46, Z = 4; beta = 108° V = 776.27 Den(Calc)= 6.42

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2₁/c

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

By Intensity(I/I_o): 2.88(1), 2.98(1), 3.31(1),

Crystal Structure:

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Cocco G , Fanfani L , Zanazzi P F , Zeitschrift fur Kristallographie , 124 (1967) p.385-397, The crystal structure of fornacite, Locality: Reneville, Congo

Physical Properties of Fornacite

Cleavage:

None

Color:

Green, Yellow, Olive green, Greenish yellow.

Density:

6.27

Diaphaneity:

Transparent to Translucent

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Aggregates - Made of numerous individual crystals or clusters.

Hardness:

2-3 - Gypsum-Calcite

Luster:

Vitreous (Glassy)

Streak:

greenish yellow

Optical Properties of Fornacite

Gladstone-Dale:

CI meas= -0.084 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.059 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1854,KPDmeas= 0.1898,KC= 0.1751
Ncalc = 2.1 - 2.12

Optical Data:

Biaxial (+), a=2.14, g=2.24, bire=0.1000, 2V(Meas)=large.

Calculated Properties of Fornacite

Electron Density:

Bulk Density (Electron Density)=5.53 gm/cc
note: Specific Gravity of Fornacite =6.42 gm/cc.

Fermion Index:

Fermion Index = 0.12
Boson Index = 0.88

Photoelectric:

PE_Fornacite= 998.15 barns/electron
U=PE_Fornacite x rElectron Density=5,520.53 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Fornacite is Not Radioactive

Fornacite Classification

Dana Class:

43.04.03.02 (43)Compound Phosphates, etc.

(43.04)(Anhydrous Compound Anions With Hydroxyl or Halogen)

(43.04.03)Vauquelinite Group

43.04.03.01 Vauquelinite Pb2Cu(CrO4)(PO4)(OH) P 2₁/n 2/m

43.04.03.02 Fornacite Pb2Cu(CrO4)(AsO4)(OH) P 2₁/c 2/m

43.04.03.03 Molybdofornacite Pb2Cu[(As,P)O4][(Mo,Cr)O4](OH) P 2₁/c 2/m

Strunz Class:

07.FC.10 07 - SULFATES (SELENATES, TELLURATES)

07.F - Chromates

07.FC -With PO4, AsO4, SiO4

07.FC.10 Fornacite Pb2Cu(CrO4)(AsO4)(OH) P 2₁/c 2/m

07.FC.10 Molybdofornacite Pb2Cu[(As,P)O4][(Mo,Cr)O4](OH) P 2₁/c 2/m

Other Fornacite Information

References:

NAME( AntBidBlaNic4) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic4)

See Also:

Links to other databases for Fornacite :
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 Fornacite here :
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Print or Cut-and-Paste your Fornacite Specimen Label here :

Fornacite

Pb2Cu(CrO4)(AsO4)(OH)
Dana No: 43.04.03.02 Strunz No: 07.FC.10
Locality:

Notes: