Cornwallite Mineral Data

Cornwallite Mineral Data +

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General Cornwallite Information

Chemical Formula:

Cu5(AsO4)2(OH)4

Composition:

Molecular Weight = 681.61 gm

Copper 46.61 % Cu 58.35 % CuO

Arsenic 21.98 % As 33.72 % As₂O₅

Hydrogen 0.89 % H 7.93 % H₂O

Oxygen 30.51 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Cu₅(AsO₄)₂(OH)₄·(H₂O)

Environment:

Dimorphous with cornubite.

IMA Status:

Valid Species (Pre-IMA) 1847

Locality:

Link to MinDat.org Location Data.

Name Origin:

Named after the English leader Cornwall.

Synonym:

Erinite

ICSD 89035

PDF 39-1357

Cornwallite Image

Images:

Cornwallite

Comments: Emerald green botryoidal crystals of cornwallite.
Location: Tintic District, Juab County, Utah, USA. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Cornwallite Crystallography

Axial Ratios:

a:b:c =3.0091:1:0.7966

Cell Dimensions:

a = 17.405, b = 5.784, c = 4.608, Z = 2; beta = 92° V = 463.61 Den(Calc)= 4.88

Crystal System:

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

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

By Intensity(I/I_o): 3.22(1), 3.1(0.9), 3.53(0.9),

Crystal Structure:

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Arlt T , Armbruster T , Neues Jahrbuch fur Mineralogie, Monatshefte , 1999 (1999) p.468-480, Single-crystal X-ray structure refinement of cornwallite, Cu5(AsO4)2(OH)4:, A comparison with its polymorph cornubite and the (PO4)-analogue pseudomalachite, Locality: Clara mine, Oberwolfach, Black Forest, Germany, Note: Biso for O2 and O4 switched to match calculated values

Physical Properties of Cornwallite

Cleavage:

None

Color:

Light green, Dark green, Black green.

Density:

4 - 4.16, Average = 4.08

Diaphaniety:

Subtranslucent

Fracture:

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

Habit:

Encrustations - Forms crust-like aggregates on matrix.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Habit:

Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)

Hardness:

4-5 - Fluorite-Apatite

Luster:

Earthy (Dull)

Streak:

apple green

Optical Properties of Cornwallite

Gladstone-Dale:

CI meas= -0.119 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= 0.064 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1692,KPDmeas= 0.2024,KC= 0.1808

Optical Data:

Biaxial (+), a=1.812, b=1.815, g=1.85, bire=0.0380, 2V(Calc)=34, 2V(Meas)=30-50.

Calculated Properties of Cornwallite

Electron Density:

r_electron=4.60 gm/cc
note: r_Cornwallite=4.88 gm/cc.

Fermion Index

Fermion Index = 0.00014
Boson Index = 0.99986

Photoelectric:

PE_Cornwallite= 35.97 barns/electron
U=PE_Cornwallite x r_electron= 165.32 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Cornwallite is Not Radioactive

Cornwallite Classification

Dana Class:

41.4.2.2 (41)Anhydrous Phosphates, etc. Containing Hydroxyl or Halogen

(41.4)where (A B)5 (XO4)2 Zq

(41.4.2)Dana Group

41.4.2.1 Cornubite Cu5(AsO4)2(OH)4 P1 1

41.4.2.2 Cornwallite Cu5(AsO4)2(OH)4 P 2₁/a 2/m

Strunz Class:

VII/B.11-40 VII - Phosphates, Arsenates and Vanadates

VII/B - Waterfree phosphates with unfamiliar anions F, Cl, O,OH, cations of medium size: Mg, Mn, Fe, Cu, Zn, Pseudomalachite group and related compounds

VII/B.11 - Pseudomalachite group, Ludjibaite - Reppiaite series

VII/B.11-10 Ludjibaite Cu5(PO4)2(OH)4 P1 1

VII/B.11-20 Pseudomalachite Cu5(PO4)2(OH)4 P 2₁/a 2/m

VII/B.11-30 Reichenbachite Cu5(PO4)2(OH)4 P 2₁/a 2/m

VII/B.11-40 Cornwallite Cu5(AsO4)2(OH)4 P 2₁/a 2/m

VII/B.11-50 Cornubite Cu5(AsO4)2(OH)4 P1 1

VII/B.11-60 Turanite Cu5(VO4)2(OH)4 P1 1

VII/B.11-65 Gatehouseite Mn5(PO4)2(OH)4 P 2₁2₁2₁ 2 2 2

VII/B.11-70 Arsenoclasite Mn5(AsO4)2(OH)4 P 2₁2₁2₁ 2 2 2

VII/B.11-80 Reppiaite Mn5[(V,As)O4]2(OH)4 C 2/m 2/m

Other Cornwallite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

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Cornwallite

Cu5(AsO4)2(OH)4
Dana No: 41.4.2.2 Strunz No: VII/B.11-40
Locality:

Notes: