What does Hypocrystalline mean?
Hypocrystalline is a textural term describing an igneous rock consisting of a mixture of glass and crystals where the ratio of crystals to glass is greater than 3:5. Rocks containing a higher ratio of glass are described as hypohaline or holohyaline.
What is the meaning of Phaneritic?
[ făn′ə-rĭt′ĭk ] Of or relating to an igneous rock in which the crystals are so coarse that individual minerals can be distinguished with the naked eye. Phaneritic rocks are intrusive rocks that cooled slowly enough to allow significant crystal growth.
What is holohyaline in geology?
holohyaline A rarely used textural term referring to igneous rocks or parts of igneous rocks which are composed entirely of glass.
Is andesite a Hypocrystalline?
Vitro-porphyry Andesite Structure: hypocrystalline, porphyry-vitreous Texture: unoriented (massive), compact.
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.
What does a porphyritic rock look like?
Porphyritic – This texture describes a rock that has well-formed crystals visible to the naked eye, called phenocrysts, set in a very fine grained or glassy matrix, called the groundmass. This texture is characteristic of most volcanic rocks.
What are the characteristics of gabbro?
Gabbro is a coarse-grained, dark-colored, intrusive igneous rock. It is usually black or dark green in color and composed mainly of the minerals plagioclase and augite. It is the most abundant rock in the deep oceanic crust.
What is porphyritic rock?
Porphyritic – This texture describes a rock that has well-formed crystals visible to the naked eye, called phenocrysts, set in a very fine grained or glassy matrix, called the groundmass. An aphanitic texture is developed when magma is erupted at the Earth’s surface and cools too quickly for large crystals to grow.
How is syenite formed?
Syenites are products of alkaline igneous activity, generally formed in thick continental crustal areas, or in Cordilleran subduction zones. To produce a syenite, it is necessary to melt a granitic or igneous protolith to a fairly low degree of partial melting.
What is Panidiomorphic?
A textural term for rocks in which all or almost all of the mineral constituents are idiomorphic or euhedral.
Is andesite an intermediate?
Andesite is an extrusive rock intermediate in composition between rhyolite and basalt. The word andesite is derived from the Andes Mountains in South America, where andesite is common. Andesite is the volcanic equivalent of diorite.