aphanitic texture
Quick Summary
Aphanitic texture in geology refers to igneous rocks where the mineral grains are too small to be seen with the naked eye, requiring magnification to observe. This fine-grained texture typically indicates that the magma cooled relatively quickly, a common characteristic of volcanic rocks. Aphanitic rocks can be further classified as microcrystalline or cryptocrystalline depending on whether their constituents are visible under a microscope. In contrast, phaneritic texture describes rocks with visible mineral grains, formed by slower cooling. The texture of an igneous rock provides valuable clues about the conditions under which it formed.1
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rockClassification by grain or crystal sizeAphanitic is a descriptive term for small crystals, and phaneritic for larger ones. Very coarse crystals (those larger than 3 centimetres, or 1.2 inches) are termed pegmatitic.
Read MoreAphanitic is a descriptive term for small crystals, and phaneritic for larger ones. Very coarse crystals (those larger than 3 centimetres, or 1.2 inches) are termed pegmatitic.
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igneous rock…aid of a microscope (called aphanitic, from the Greek aphanēs, meaning “invisible”) or contains no minerals at all (in the latter case, the rock is composed of glass, which is a highly viscous liquid). This results in two groups: (1) plutonic intrusive igneous rocks that solidified deep within the crust…
Read More…aid of a microscope (called aphanitic, from the Greek aphanēs, meaning “invisible”) or contains no minerals at all (in the latter case, the rock is composed of glass, which is a highly viscous liquid). This results in two groups: (1) plutonic intrusive igneous rocks that solidified deep within the crust…
Read More- igneous rockCrystallinity
Aphanitic rocks are further described as either microcrystalline or cryptocrystalline, according to whether or not their individual constituents can be resolved under the microscope. The subaphanitic, or hyaline, rocks are referred to as glassy, or vitric, in terms of granularity.
Read MoreAphanitic rocks are further described as either microcrystalline or cryptocrystalline, according to whether or not their individual constituents can be resolved under the microscope. The subaphanitic, or hyaline, rocks are referred to as glassy, or vitric, in terms of granularity.
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