BorniteBy: Marina Meyers

Bornite is an important copper ore mineral. Bornite is usually lacking good crystals. They are rare and so bornite is commonly known as simply a massive mineral ore.

It is Made of Cu2FeS4.

Its hardness is at 3.

The color is brown to black with a typical purplish-bluish tarnish, a reddish bronze color on freshly broken surfaces.

Its luster is Metallic.

Its streak is a gray black color.

Its Density is approximately 4.9 - 5.3 (average for metallic minerals).

Its crystal structure is only isometric at temperatures above 228ÂșC and it was above this temperature that the crystals formed. As bornite cooled it structurally altered to possibly a tetragonal structure but outwardly it retained the isometric forms.

Its cleavage is very poor, (octahedral) and its fracture is conchoidal.

Its special characteristic is the tarnish that occurs on fresh surfaces can form in hours, but it will become black over time.

It forms in hydrothermal veins with minerals such as quartz, chalcopyrite, and galena. It also forms in some igneous rocks. The oxidation zone of copper veins can contain bornite.

It is found in Bristol, Conecticut, Butte, Montana, Plumas Co., Colorado and Superior, Arizona, USA; Cornwall, England; Rhineland, Germany; Tsumeb, Namibia; South Africa; Morocco; Bolivia; Chile; Peru and Mexico.

It is sometimes used as an ore for copper and sold to amateur miners and collectors.

It is not found in Iowa, but it is found in many other places in the Unites States of America and other countries.


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