Bornite (peacock stone): meaning, iridescent ore, precautions

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Bornite is a copper ore whose surface tarnishes into blue, violet and red. Many "peacock stones" sold are chalcopyrite treated with acid.

Key points

Colour	coppery brown on a fresh break; iridescent blue, violet and red after tarnishing
Mineral family	copper and iron sulfide, Cu5FeS4
Hardness (Mohs)	about 3 to 3.25: soft
Copper content	about 63% by mass
Origin of the name	given in 1845 in honour of the Austrian mineralogist Ignaz von Born
Known deposits	Montana, Connecticut (United States), Cornwall, Tyrol, Zimbabwe, Morocco, Tasmania, Kazakhstan
Nickname	"peacock stone" or "peacock ore"
Precautions	contains copper and sulfur: not in the mouth, no elixirs, wash hands, avoid dust

What is bornite?

Bornite is a copper ore: a copper and iron sulfide (Cu5FeS4) containing about 63% copper by mass. It has been described since 1725 in the Metalliferous Mountains of Bohemia; its current name dates from 1845 and honours the Austrian mineralogist Ignaz von Born. It is soft (about 3 to 3.25 on the Mohs scale).

On a fresh break, it is coppery brown. When exposed to air, it tarnishes within days or weeks and takes on iridescent blue, violet, red and green reflections: this is what earned it the nickname "peacock ore". It is mined notably at Butte (Montana), in Cornwall, in the Tyrol, in Zimbabwe, in Morocco, in Tasmania and in Kazakhstan.

Since it is used to produce copper, it is found in copper mines around the world. Its "ornamental stone" version is a by-product of this activity.

Warning: the "peacock stone" is often something else

This is the most important point on this page. According to several mineralogy websites, most of the "peacock ore" sold to collectors and tourists is actually chalcopyrite (another copper and iron sulfide, see chalcopyrite) whose surface has been treated with acid to produce a very colourful tarnish. This treatment imitates a natural process, but gives far brighter and more even colours than those of natural bornite.

This is not a fault in itself, provided it is disclosed. When a listing says "bornite" without further detail, nothing tells you which mineral it is without analysis. If the colour is extremely bright, uniform and contrasted, it is probably the result of treatment.

The coloured layer, natural or treated, is superficial: it can wear away, oxidise further or change over time.

Traditional symbolism

The peacock is an animal laden with symbols in many cultures: beauty, renewal, vigilance (its feathers bear "eyes"). By extension, bornite is associated with joy, creativity and transformation (its colours change with the angle).

This symbolism is recent and comes from the stone's colours. There is no ancient tradition for bornite as an ornamental stone. No study shows any effect on health, mood or luck.

Traditional correspondences

Area	Correspondence cited
Chakra	sacral and solar plexus; sometimes all chakras (through its colours)
Element	earth (ore) or fire
Signs	no consensus
Keywords	joy, creativity, change

These links, taken from modern crystal literature, are given for information only. See the sacral chakra.

Safety: a copper ore

Never in the mouth and never in an elixir: copper minerals can release copper into solution, which is irritating or toxic in quantity.
Hands: wash them after handling the stone, especially before eating.
Dust: do not saw, file or heat the stone. Copper sulfide fumes are dangerous.
Acids: do not immerse it in vinegar or any acidic product: you would destroy it and obtain a copper solution.
Children and animals: keep it out of their reach.
Skin: prolonged contact may leave a greenish mark on some sensitive people. This is not dangerous in itself.

How to use it

As a collector's piece: a small rough piece in a display case, away from moisture.
As a tumbled stone or cabochon: the stone is soft; a piece of jewellery must be protected. See the jewellery guide.
As an object of observation: watch the colours change under the light.

Care

Water: avoid it, or limit yourself to a barely damp cloth, followed by immediate drying. Humidity speeds up tarnishing.
Chemical products: no abrasive soap, perfume or acid.
Sun and heat: to be avoided.
Storage: dry, separately, in a cloth or small box.
Symbolic cleansing: smoke or sound rather than water and salt (see the guide).

Recognising and choosing

Natural bornite shows uneven iridescent reflections, on a coppery brown background visible where the surface is chipped. Acid-treated pieces have very bright, even colours, often red, blue and violet over the whole surface. Ask for the words "treated" or "tarnished" to appear in the listing. Rough bornite pieces are inexpensive; shaped pieces cost more but remain fragile. To compare with another iridescent sulfide, see bismuth or chalcopyrite. For other guidance, read real or fake stone.