Amphibole facts for kids

Amphibole (Tremolite)

Amphibole is the name for a large group of minerals. These minerals are known as inosilicates. This means they are built from chains of silicon and oxygen. Amphiboles often form crystals that look like prisms or long needles.

They are made of double chains of SiO₄ units. These units are called tetrahedra because they have four sides. These tetrahedra link together at their corners. Amphiboles usually contain ions of iron and/or magnesium inside their structures. These minerals can be many different colors. You might find them in green, black, colorless, white, yellow, blue, or brown.

What Are Amphiboles?

Amphiboles are a very common type of mineral. They are found in many different kinds of rocks. These rocks include igneous rocks, which form from cooled lava, and metamorphic rocks, which change due to heat and pressure. Think of them as tiny building blocks of the Earth's crust.

How Do They Form?

Amphiboles usually form when hot, watery fluids are present. This often happens deep inside the Earth. They can also form when existing rocks are changed by heat and pressure. This process is called metamorphism. The specific conditions, like temperature and pressure, decide which type of amphibole will grow.

What Are Their Properties?

Amphiboles have some interesting features.

• Crystal Shape: They often grow as long, thin crystals. These can look like needles or columns.
• Hardness: Most amphiboles are fairly hard. They can scratch glass.
• Cleavage: They break along flat surfaces in a specific way. This is called cleavage. Amphiboles usually break at angles of about 56 and 124 degrees. This can help scientists identify them.
• Color: As mentioned, their colors vary a lot. The color often depends on the specific metals inside them. For example, iron can make them look dark.

Types of Amphiboles

There are many different kinds of amphiboles. They are all part of the same group but have slightly different chemical makeups. Some common examples include:

• Tremolite: This amphibole is often white or light-colored. It is sometimes found in marble.
• Hornblende: This is one of the most common amphiboles. It is usually dark green or black. You can find it in many igneous and metamorphic rocks.
• Actinolite: This mineral is often green. It is found in metamorphic rocks.
• Glaucophane: This amphibole is known for its blue color. It forms under very high pressure and low temperature conditions.

Where Are Amphiboles Found?

Amphiboles are found all over the world. They are important parts of many mountain ranges. You can find them in places where volcanoes have been active. You can also find them where rocks have been deeply buried and changed. They are common in rocks like granite, basalt, and amphibolite.

Images for kids

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  Photomicrographs of a thin section containing an amphibole crystal; under cross-polarized light on the left, and plane-polarized light on the right.

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  Hornblende diorite from the Henry Mountains, Utah, US

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  Amphibolite from Warrensburg, Adirondack Mountains, New York State, USA

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  Double-chain inosilicate structure looking up the [100] axis. Silicon ions are hidden by apical oxygen ions.

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  Side view (along [010]) of double chain inosilicate backbone. Apical oxygens are at the bottom.

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  Amphibole structure looking along the [001] axis. Silicon ions are emphasized. Two "I-beams" are outlined in green.

See also

In Spanish: Anfíbol para niños