What is leucocratic rock?

What is leucocratic rock?

Definition of leucocratic of a mineral or rock. : having a light color — compare melanocratic, mesocratic.

What is the classification of igneous rocks based on?

Igneous rocks may be simply classified according to their chemical/mineral composition as felsic, intermediate, mafic, and ultramafic, and by texture or grain size: intrusive rocks are course grained (all crystals are visible to the naked eye) while extrusive rocks may be fine-grained (microscopic crystals) or glass ( …

What is Panidiomorphic texture?

Panidiomorphic refers to a texture in which, theoretically all the component mineral grains are subhedral. Allotriomorphic refers to a texture in which all the component mineral grains are anhedral.

Is quartz an Aphanitic?

Aphanites are commonly porphyritic, having large crystals embedded in the fine groundmass, or matrix. The larger inclusions are called phenocrysts. They consist essentially of very small crystals of minerals such as plagioclase feldspar, with hornblende or augite, and may contain also biotite, quartz, and orthoclase.

What are the 4 compositions of igneous rocks?

As has already been described, igneous rocks are classified into four categories, based on either their chemistry or their mineral composition: felsic, intermediate, mafic, and ultramafic.

What are the six major igneous rock textures?

Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic.

What is the types of igneous rock?

The two main categories of igneous rocks are extrusive and intrusive. Extrusive rocks are formed on the surface of the Earth from lava, which is magma that has emerged from underground. Intrusive rocks are formed from magma that cools and solidifies within the crust of the planet.

What is Panidiomorphic?

/ (pæˌnɪdɪəʊˈmɔːfɪk) / adjective. (of igneous rocks) having well-developed crystals. GOOSES.

What is the main difference between phaneritic and aphanitic rocks?

APHANITIC TEXTURE – Igneous rocks that form on the earth’s surface have very fine-grained texture because the crystals are too small to see without magnification. PHANERITIC TEXTURE – Igneous rocks with large, visible crystals because the rock formed slowly in an underground magma chamber.

What is an aphanitic rock?

rocks. In rock: Classification by grain or crystal size. Aphanitic 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.

Is granite an Aphanitic?

Granite, the most well known example of an intrusive igneous rock, has a phaneritic texture.

What are the 4 igneous rock compositions?