Advertising Information

Classic Chalcocite from Bristol

The Mineral chalcocite




Chalcocite is a coveted and iconic mineral among collectors. Specimens from classic and extinct localities, such as Cornwall, England and Bristol, Connecticut, will command extremely high prices, especially when in good crystals. Chalcocite forms from the alteration of other minerals, especially other copper sulfides such as Bornite, Covellite, and, Chalcopyrite, and may also form pseudomorphs after these minerals. It often forms in association withChrysocolla, with the Chrysocolla forming as an alteration around the Chalcocite. Chalcocite is named after the Greek word chalcos, which means "copper" in Greek, in allusion to the copper content in this mineral.
Chemical Formula Cu2S
Composition Copper sulfide
Color Gray to black, often with a bluish tinge. Occasionally iridescent.
Streak Dark gray. Streak may be shiny.
Hardness 2.5 - 3
Crystal System Orthorhombic
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
Crystals are tabular, and may be pseudohexagonal in shape. They may be in dense, random aggregates of thin crystals or almost snowflake in nature. Also in bent twins of prismatic crystals and in sixlings. Elongated crystals and groups of elongated crystals do occur, but this is rare. Also occurs platy, grainy, and massive. Crystals are commonly striated.
Transparency Opaque
Specific Gravity 5.5 - 5.8
Luster Metallic
Cleavage 3,1
Fracture Conchoidal
Tenacity Brittle
Other ID Marks May develop a thin film layer on crystal faces.
Complex Tests Soluble in nitric acid.
In Group Sulfides; Simple Sulfides
Striking Features Heaviness and crystal forms
Environment Formed in copper deposits, usually as a secondary mineral in the oxidized zone, and often as an alteration of primary copper minerals in ore veins. Also found in volcanic basalt deposits.
Rock Type Igneous, Metamorphic
Popularity (1-4) 2
Prevalence (1-3) 2
Demand (1-3) 1

Chalcocite ON EBAY

VARIETIES
 -  Chalcocite coating or pseudomorph over Pyrite.
 -  Chalcocite from the Redruth area in Cornwall, England.

USES
Chalcocite is an important copper ore. It has a high copper content and the process of extracting the copper from the sulfur in Chalcocite is relatively easily. Chalcocite is also an important collector's mineral, and good crystals command very high prices.

NOTEWORTHY LOCALITIES
In Europe, the most classic occurrence is Cornwall, England. Several well-known Cornish localities are the Carn Brea area; the Geevor Mine; the Levant Mine; and St Ives. Two African occurrences of note are Tsumeb, Namibia; and Shaba, Congo (Zaire). A relatively new Asian occurrence is Dzhezkazgan, Kazakhstan. Large, well-formed crystals come from the Mammoth Mine, Mount Isa, Queensland, Australia

In the U.S., the best crystals once came from the old mine operations at Bristol, Hartford County, Connecticut. Another classic Chalcocite locality is Butte, Silver Bow Co., Montana. A new finding in the 1990's in the Flambeau Mine, Ladysmith, Rusk Co., Wisconsin, has yielded some excellent specimens. Other notable U.S. finds are the Santa Rita Mine, Grant Co., New Mexico; Bisbee, Cochise Co., Arizona; and the Chimney Rock Quarry, Bound Brook, Somerset Co., New Jersey.

COMMON MINERAL ASSOCIATIONS
Chrysocolla, Malachite, Bornite, Calcite, Galena, Quartz

DISTINGUISHING SIMILAR MINERALS
Galena - Different crystals and cleavage.
Acanthite - Is more sectile.


chalcocite PHOTOS
 
ADDITIONAL RESOURCES
 
DISCUSSIONView Forum | Post to Forum
Have a question about Chalcocite? Visit our Q&A Community and ask the experts!
PAGE SPONSOR  

To sponsor this page, click here.

Let us know how we can update this page
(Click for more details)
We strive for accurate content and locality information. If you feel any of the content is incorrect, or if you feel we are missing vital locality information, please fill out the form below so we can update the site. If you are requesting a locality be added, please only include significant locality occurences for the mineral.