WebIn geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. WebFine-grained ("volcanic") crystalline igneous rock that have mineral grains mostly <2mm, not readily identifiable to the naked eye. The subtypes usually must be petrographically and/or chemically analysed and plotted on QAPF …

4.1: Classification of Igneous Rocks - Geosciences LibreTexts

Webigneous: [adjective] of, relating to, or resembling fire : fiery. WebCrystallinity The degree of crystallization attained by an igneous rock is measured by the relative amounts of crystallized and glassy portions. All degrees of crystallinity are known to exist, from perfectly glassy rocks, through those consisting of glass with more or less crystals, to completely crystalline rocks. gravity live tab

5.2: Igneous Rock Identification - Geosciences LibreTexts

WebA complex aluminous silicate of calcium, iron and magnesium, crystallising in the monoclinic system, and occurring in many igneous rocks, particularly those of basic composition. It is an essential component of basalt, dolerite and gabbro. aureole A zone surrounding an igneous intrusion in which country rock shows effects of contact metamorphism. WebAccording to the texture of the grains, igneous rocks may be classified as pegmatitic: very large crystals phaneritic: rocks contain minerals with crystals visible to the unaided eye, commonly intrusive aphanitic: rapid cooling, crystal nucleation and growth is stunted, forming a uniform, fine grained rock WebIgneous rocks are common in the geologic record, but surprisingly, it is the intrusive rocks that are more common. Extrusive rocks, because of their small crystals and glass, are less durable. Plus, they are, by definition, … chocolate chip layered dessert