Click on a letter above to view the list of gems.    

Cornetite  
Current inventory:  0 gems
 

  
Cornetite was named to honor Jules Cornet (1865–1929), 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 H₂O
E : With only medium-sized cations, (OH, etc.):RO₄ > 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 (Zaïre)

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 Copiapó, 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:

We have not photographed our Cornetite gems. Please check back soon.