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Cornetite  
Current inventory:  0 gems
 

Cornetite

  
Cornetite was named to honor Jules Cornet (1865ľ1929), Belgian geologist.

Discovered in 1916.   IMA status: Valid (pre-IMA; Grandfathered)

 

Chemistry

 

 

Chemical Formula:

Cu3(PO4)(OH)3

 

Copper Phosphate Hydroxide

Molecular Weight:

336.63 gm

Composition:

Copper

56.63 %

Cu

70.89 %

CuO

 

Phosphorus

9.20 %

P

21.08 %

P2O5

 

Hydrogem

0.90 %

H

8.03 %

H2O

 

Oxygen

33.27 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Phosphates

Strunz 8th Ed. ID:

7/B.13-10

Nickel-Strunz 10th Ed. ID:

8.BE.15

 

8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H
2O
E : With only medium-sized cations, (OH, etc.):RO
4 > 2:1

 

 

Crystal Data

   

   

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

As crystals, short prismatic on [001], {210} rounded, also showing large {021}, {221}, with a number of other forms known, to 1 cm; as flat radial aggregates and crusts.

Twinning:

On {h0l}.

 

 

Physical Properties

   

 

Cleavage:

None observed

Fracture:

n/a

Tenacity:

Brittle

Moh's Hardness:

4.5

Density:

4.1 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Soluble in cold HCl.

 

 

Optical Properties

   

   

Color:

Dark Blue to Green-Blue; Green-Blue in transmitted light. May exhibit colour zoning in shades of green-blue.

Transparency:

Translucent to Transparent

Luster:

Vitreous

Refractive Index:

1.765 - 1.820  Biaxial ( - )

Birefringence:

0.0550

Dispersion:

Strong; r < v

Pleochroism:

None

 

 

Occurances

   

   

Geological Setting:

A rare secondary mineral in the oxidized zone of some hydrothermal copper deposits.

Common Associations:

Copper, Brochantite, Pseudomalachite, Libethenite, Malachite, Atacamite, Chrysocolla, Heterogenite.

Common Impurities:

Co

Type Locality:

L'Etoile du Congo Mine (Star of the Congo Mine; Kalukuluku Mine), Lubumbashi (Elizabethville), Southern area, Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo (Za´re)

Year Discovered:

1916

View mineral photos:

Cornetite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Cornetite is a rare secondary copper mineral that is an attractive deep blue to green-blue color. Crystals are very small and typically found as flat radial aggregates and crusts. A faceted gem would be a true rarity. Mineral specimens have been cut as cabochons for gem collectors.

Cornetite is found in several notable localities including from the Star of the Congo mine, near Lubumbashi, and at the Kalabi and Lukini mines, Katanga Province, Congo (Shaba Province, Zaire). From the Bwana Mkubwa mine, Ndola, and Kansanshi, Zambia. At the Alaska, Mangula, and Molly mines, Lomagundi district, Zimbabwe. In the USA, in the Blue Jay and Empire-Nevada mines, Yerington district, Lyon County, Nevada; at Tyrone, Santa Rita, Grant County, New Mexico; on Saginaw Hill, Pima County, Arizona. From Cerro Verde, Sonora, Mexico. In Chile, at Chuquicamata, Antofagasta; the Manto Ruso mine, about 85 km north of Copiapˇ, Atacama; and the Brillador mine, La Serena, near Coquimbo. From the Blockade mine, 60 km east of Mount Isa, and at Ravenswood, Queensland, Australia.
 

  
Cornetite gems for sale:

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