Esquel

A Patagonian pallasite whose glowing golden-green crystals have made it one of the most beautiful meteorites ever found.

Key facts

Type

Stony-iron, pallasite (main group)

Fell or found

Found

Year

1951

Country

Argentina

Mass

about 755 kg

Official name

Esquel

In 1951, a farmer in the province of Chubut, in Argentine Patagonia, was digging a hole to put up a windmill when he struck a large, heavy mass. It was a meteorite weighing about 755 kilograms. When it was later cut and polished, it revealed one of the most spectacular interiors of any meteorite on Earth: a framework of shining metal holding large, glassy crystals that glow golden green when light shines through them. Its name comes from the nearby town of Esquel.

What is a pallasite?

Esquel is a pallasite, one of the rarest and most beautiful types of meteorite. Pallasites are stony-iron meteorites: roughly half metal and half stone. The metal is an alloy of iron and nickel, and the stone is almost entirely the mineral olivine, a magnesium-iron silicate. Gem-quality olivine is known as peridot, and in some pallasites, including Esquel, the crystals are clear enough to be cut as gemstones.

Pallasites are named after Peter Simon Pallas, a German naturalist working in Russia, who described the first known example in the 18th century, a mass found in Siberia now known as Krasnojarsk.

Where do pallasites come from?

For many years scientists thought pallasites formed at the boundary between the metal core and the rocky mantle of a melted asteroid. In this picture, olivine from the lower mantle became mixed with molten metal from the core, and the mixture cooled very slowly. More recent studies have suggested other possibilities, such as violent collisions that drove molten metal from one body into the olivine-rich mantle of another, or mixing at shallower depths. What is clear is that pallasites record a time when asteroids were partly molten, and that they cooled slowly enough for their metal to form the Widmanstätten pattern, an interlocking network of metal crystals that appears when a polished surface is etched.

Esquel belongs to the main group of pallasites, which share very similar chemistry and probably come from a single parent body, or from closely related ones.

A meteorite worth slicing

Esquel is famous for its large, angular olivine crystals, many of them a centimetre or more across, and for being unusually stable. Many pallasites rust and crumble when cut, because moisture attacks the metal and minerals along their cracks. Esquel has proved more durable, which is one reason why thin, polished slices of it are so admired. When a slice is held up to the light, the olivine crystals glow like stained glass set in a silver frame. Slices of Esquel are displayed in museums around the world.

Cutting and polishing meteorites is skilled work done by specialists with proper equipment. It is never something to attempt at home, and children should not cut, heat or put chemicals on any rock they think might be a meteorite.

Why it matters

Pallasites like Esquel offer a rare glimpse of the deep interior of a planetary body. On Earth, the boundary between the core and the mantle lies nearly 3,000 kilometres below our feet, far beyond the reach of any drill. In pallasites, material from a comparable zone, or from a dramatic collision between metal and rock, can be held in the hand.

Esquel also shows how much luck plays a part in meteorite discoveries. Had the farmer chosen a spot a few metres away for his windmill, one of the world's most beautiful meteorites might still be buried beneath the Patagonian grasslands.

Next time you see a polished slice of a pallasite, look closely at the colours of the crystals and the way they sit in the metal. You are looking at a scene that formed deep inside a small world in the first few million years of the Solar System.

Did you know?

See more

Esquel in the catalogue