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Cassiterite

earth science Maturity 7-9 Next article →

Cassiterite is a special mineral used to find tin. It is a tin oxide, which means tin is mixed with oxygen.

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Rutile-unit-cell-3D-balls

This mineral is very important for our world. It was the main source of tin in ancient history. Today, it remains the most important source of this metal. Some crystals of cassiterite even look like beautiful gems. They have many flat faces that catch the light. Thin crystals can even let light pass through them.

Finding and moving this mineral is a unique way it works. Cassiterite is very heavy compared to other rocks. It has a specific gravity of about 7.0. This means it is much denser than many common stones. Miners use a method called hydraulic mining to find it. They use water to wash away lighter materials. The heavy tin ore stays behind because of its weight. This helps people concentrate the ore for use.

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Rutile-unit-cell-3D-balls

People have been looking for this mineral for a long time. In England, people worked in Cornwall and Devon 4,500 years ago. They found cassiterite in high temperature quartz veins. These veins also held other minerals like topaz and fluorite. The name comes from the Greek word "kassiteros" for tin. You can even find mentions of tin in Homer's Iliad. This ancient poem describes the Shield of Achilles. It even mentions greaves made of pliant tin.

Rutile-unit-cell-3D-balls
Rutile-unit-cell-3D-balls

There are many places on Earth where we find cassiterite. Much of it comes from placer deposits in river beds. These are found in Malaysia, Thailand, and Indonesia. It is also found in Russia and the Maakhir region of Somalia. Some of the best primary sources are in Bolivia. There, it grows in hydrothermal veins. In the Democratic Republic of the Congo, fighting over these deposits is a major cause of conflict. This has led to it being called a conflict mineral.

Rutile-unit-cell-3D-balls
Rutile-unit-cell-3D-balls

When you look at these crystals, you might see strange shapes. Many pieces show something called crystal twinning. This happens when crystals grow together in a specific way. A common type is called an "elbow twin." These look like they are bent at a 60-degree angle. Another type is called wood tin. This type has a shape called botryoidal or reniform. It looks a bit like a cluster of grapes. Collectors love to find these unique pieces.

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Rutile-unit-cell-3D-balls
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