These are igneous rocks that are too fine textured to an extent that there mineral grains or crystalline texture cannot be seen or distinguished with the necked or unaided eyes. They appear or occur as a whole single massive crystalline extrusive body of Igneous origin. Example is Obsidian.
A term that describes an igneous rock texture with crystals that are present but not visible would be aphanitic. This texture indicates that the individual mineral grains are too small to be distinguished with the naked eye.
And their texture, which can be aphanitic, phaneritic, glassy, or porphyritic. mineral composition and crystal texture
Rhyolite forms when the felsic magma (greater than 63% SiO2 by weight) came out to the earth surface and can be identified by its aphanitic texture ( The individual crystals in an aphanitic igneous rock are not distinguisable to the naked eye)
Basalt is an extrusive igneous rock formed from the rapid cooling of lava, with a fine-grained texture and dark color due to high concentrations of iron and magnesium. Granite is an intrusive igneous rock formed from the slow cooling of magma underground, with a coarse-grained texture and lighter color due to its composition of quartz, feldspar, and mica. Both rocks are composed of silicate minerals, have crystalline structures, and are commonly used in construction and architecture.
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The texture thus described is referred to as aphanitic texture.
The rock is said to be extrusive or possess an aphanitic texture, as a result of relatively rapid cooling.
These are extrusive igneous rocks with an aphanitic texture.
A term that describes an igneous rock texture with crystals that are present but not visible would be aphanitic. This texture indicates that the individual mineral grains are too small to be distinguished with the naked eye.
And their texture, which can be aphanitic, phaneritic, glassy, or porphyritic. mineral composition and crystal texture
Rocks with an aphanitic texture have fine-grained crystals that are too small to be seen by the naked eye. Common igneous rocks with this texture include basalt, andesite, and rhyolite. These rocks cool quickly at the Earth's surface, preventing larger crystals from forming.
The rock is said to have a fine-grained texture, also referred to as an aphanitic texture.
Small crystal grains form when molten rock cools quickly. In an extrusive igneous rock, it's referred to as aphanitic texture.
The size of the mineral crystals in an igneous rock determines the rock's texture.
Rhyolite forms when the felsic magma (greater than 63% SiO2 by weight) came out to the earth surface and can be identified by its aphanitic texture ( The individual crystals in an aphanitic igneous rock are not distinguisable to the naked eye)
A texture that would most unlikely occur in an extrusive igneous rock is a coarse-grained or phaneritic texture. This texture, characterized by large, visible crystals, typically forms in intrusive igneous rocks where the magma cools slowly beneath the Earth's surface. In contrast, extrusive igneous rocks cool quickly at or near the surface, resulting in fine-grained or glassy textures, such as aphanitic or vitreous. Consequently, the formation of large crystals in extrusive rocks is highly improbable.
*fine-grained *coarse-grained