What is Covellite?
Covellite is an indigo-blue copper sulfide known for metallic lustre, iridescent tarnish and striking associations with other copper minerals.
Mineralogy and structure
The reference formula is CuS. Covellite belongs to the sulfides and has a hexagonal crystal system. Covellite is hexagonal and very soft. Its vivid blue colour and iridescent surface make it attractive to collectors, but the mineral is usually fragile and best kept as a labelled display specimen.
Colour and appearance
Typical colours include indigo blue, blue-black, violet-blue. Crystal habit, lustre, transparency and matrix association are often as diagnostic as colour.
Formation and localities
Covellite forms in or is associated with secondary enrichment zones and hydrothermal copper deposits, commonly replacing earlier copper sulfides. Important documented localities include Butte in Montana, Mount Vesuvius, Italy, Tuscany, Chile and many copper districts worldwide.
Collecting and care
Covellite is best kept as a labelled collector or reference specimen. Protect fragile crystals from impact and prolonged humidity changes. Lead-, arsenic-, chromium- and cobalt-bearing minerals should not be cut, ground or used in jewellery.
