The structure of igneous rocks refers to the degree of crystallization, particle size, particle shape, particle orientation and the relationship between particles of the substances that make up igneous rocks.
Among them, crystallinity refers to the proportion of crystalline and amorphous parts in rocks. It is divided into three levels: full crystal structure, glassy structure and semi-crystal structure.
Cryptocrystalline texture belongs to a complete crystal structure, which is different from obvious crystal structure. Only under the microscope can it distinguish mineral particles, which are generally owned by hypabyssal rocks and extrusive rocks, such as felsic rocks.
Extended data:
According to the size of mineral particles, it can be subdivided into the following two structures:
1, microcrystalline structure
Microcrystalline texture refers to the crystal structure that can only be seen under a microscope. The particle size of main mineral particles is D.
2. Microscopic cryptocrystalline structure
Microscopic cryptocrystalline structure refers to the structure that the crystal is too small to distinguish the grain boundaries under the microscope. This structure is developed in volcanic rocks and rocks affected by strong impermeability.
3. Glass structure
A structure in which rocks are almost entirely composed of amorphous volcanic glass, which is found at the edge of volcanic lava and some hypabyssal and ultrahypabyssal intrusive rocks (condensation edge, etc.). ), such as obsidian.
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