KOMPAS.com – Andesite is an outer igneous rock composed of fine particles and has a dark gray color. Its mineral composition is in between granite and basalt. Andesite is a stone that is often used in construction, such as temples.
Andesite rocks are formed from deposits of lava flows produced by stratovolcanoes. This lava will quickly harden when exposed to surface temperatures. Therefore, these rocks include extrusive rocks or igneous rocks outside.
Andesite rocks are found in stratovolcanoes in subduction zones. Andesite comes from the name of a mountain in South America, namely Mount Andes. Other examples of stratovolcanoes in subduction zones can be found in Central America, Mexico, Washington, Oregon, Japan, Indonesia, the Philippines, and New Zealand.
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Andesite rock composition
Andesite rocks are not only composed of fine minerals, but also small crystals. However, these crystals are difficult to see without aids such as a magnifying glass or microscope.
Many materials contained in andesite rocks include:
- Plagioclase feldspar
- Biotite in small quantities
Differences in the color of andesite rocks may occur due to differences in the composition of their constituents. Most andesite rocks are gray, but there are variations to reddish. This color indicates a higher silica content.
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In addition to minerals, there are also crystals that make up andesite rocks. There are two kinds of crystals in andesite rocks.
- Phenorchis: large crystals that have formed beneath the Earth’s surface
- Groundmass: crystals that form rapidly on the surface.
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