Magnetite: Meaning, Properties, Lodestone and Care

What Is Magnetite?

Magnetite is an iron oxide with the formula Fe3O4, containing both divalent (II) and trivalent (III) iron. It crystallises in the cubic system, often as octahedra (two pyramids joined at their base), with a black metallic lustre. It has a hardness of 5.5 to 6.5 on the Mohs scale and is very dense (5.17 to 5.18): a small piece feels heavy in the hand.

Its main feature: it is ferrimagnetic. A magnet attracts it, and some pieces have themselves become natural magnets. It is one of the main iron ores: it contains about 72% iron by mass, which makes it highly sought after by industry. It is found in igneous and metamorphic rocks, in ancient sea floors turned into rock (banded iron formations), and in the black sands of beaches and dunes, where a magnet gathers it.

The best-known deposits are those of Kiruna in Sweden, northern Chile, the Urals in Russia, the Adirondacks and Arkansas in the United States, and Piedmont in Italy. It also often occurs together with haematite, another iron oxide, which is not magnetic or only barely so.

Lodestone and the Origin of the Name

A lodestone (pierre d'aimant in French) is a piece of magnetite that is naturally magnetised and attracts small iron objects. The ancients already knew it: the Greek philosopher Thales of Miletus, around 600 BCE, is said to have mentioned it, according to later texts. The word "magnetite" comes from the Greek magnêtis lithos, "stone of Magnesia". We do not know which of the Magnesias of antiquity (in Thessaly or in Lydia) gave its name to the stone, and the legend of the shepherd Magnes, reported by Pliny, is generally regarded as a popular explanation.

How does a rock become a magnet? The most often suggested hypothesis is lightning: a bolt magnetises the rock abruptly. This has not been demonstrated for every case, and other processes are possible.

Lodestone was used to make the first compasses, in China and then in Europe: a needle rubbed on the stone becomes magnetised. Precise dates vary between sources; it is generally accepted that the navigational compass is attested in China around the 11th century and in Europe in the 12th century.

Traditional Symbolism

A mineral that attracts iron without touching it has always struck the imagination. Modern books on crystals associate magnetite with attraction, balance and grounding, by analogy with the Earth's magnetic field and with the idea of "drawing toward oneself" what one wishes for.

These ideas are modern conventions of lithotherapy. In older popular traditions, lodestone served as a love charm, a talisman or a magical object, with very different uses across periods. No study shows any effect of the stone on health or luck. Reviews of studies on so-called "therapeutic" magnets have not concluded that any effect is demonstrated: consult a healthcare professional for any pain.

Safety: Magnets and Small Objects

• Pacemakers and medical devices: as a precaution, keep any magnetised stone or magnet away from these devices. If in doubt, ask your doctor.
• Cards and devices: a lodestone can erase a magnetic stripe and disturb a compass. Keep it away from payment cards and discs.
• Children and animals: small magnetised pieces that are swallowed can be dangerous; keep them out of reach.
• Dust: if you sand or saw the stone, wear a mask and wash your hands afterwards.
• No elixirs: do not leave the stone soaking in a drink (crystal elixirs).

How to Use It

• In a collection: an octahedron or a cluster of crystals, displayed with a small magnet to show the attraction.
• Simple experiment: bring a magnet close to a sample of black beach sand: the magnetite grains gather on the magnet. Safe, to be done with a child under supervision.
• As a pocket stone: a heavy, polished pebble held in the hand (see meditating with a stone).
• As jewellery: rare with real magnetite; most "magnetic" stone jewellery is made of hematine (see below).

Care and Cleansing

• Cleaning: a soft cloth, dry or barely damp. Excess water can leave rust on a polished or cracked stone; always dry it thoroughly.
• Salt and acids: avoid them (they corrode iron).
• Heat: at high temperature (above 580 °C), magnetite loses its magnetisation; the heat of a radiator is not enough, but avoid heat sources.
• Knocks: a knock or a fall can weaken the magnetisation of a lodestone.
• Symbolic cleansing: sound or smoke rather than water (guide).

Recognising Genuine Magnetite

Hematine (or "magnetic haematite") is a manufactured material, generally a ceramic based on iron oxides, sold as beads and jewellery; it is not magnetite. The magnet and powder test on a hidden area distinguishes these materials well, but it does not replace a laboratory opinion if the piece is expensive. See real or fake stone and our commitments.

How to Choose

For a collection, choose sharp crystals (well-formed octahedra) or a lodestone that really attracts. Well-formed crystals cost more than rough pieces. For jewellery, check the material: if the label says "magnetic haematite" or "hematine", it is a manufactured material and very affordable. Pairings: with haematite, pyrite or black tourmaline for a set of dark stones. Also read the guide to choosing and caring for your stones.

Frequently asked questions

Also read

The meanings mentioned belong to tradition and symbolism. They are neither promises of results nor medical advice. Back to Guide to stones.