aphanite
Sign in to saveAlso known as aphanitic rocks
thumb|The smooth texture of this basaltic [[volcanic bomb is aphanitic.]] thumb|upright=1.3|IUGS classification of aphanitic extrusive [[igneous rocks according to their relative alkali (Na2O + K2O) and silica (SiO2) weight contents. Blue area is roughly where alkaline rocks plot; yellow area where subalkaline rocks plot.]] thumb|An aphanitic volcanic sand grain, with fine-grained matrix (geology)|groundmass, as seen through a [[petrographic microscope]]
Wikidata facts
- Subclass of
- igneous rock
- Image
- VolcanicBombMojaveDesert.JPG
Show 3 more facts
- described by source
- Encyclopædia Britannica 11th edition
- opposite of
- phanerite
- has characteristic
- aphanitic texture
Sources (1)
via Wikidata · CC0
~2 min read
Encyclopedic overview
3 sectionsContents
- Common rocks that can be aphanitic
- See also
- References
thumb|The smooth texture of this basaltic [[volcanic bomb is aphanitic.]] thumb|upright=1.3|IUGS classification of aphanitic extrusive [[igneous rocks according to their relative alkali (Na2O + K2O) and silica (SiO2) weight contents. Blue area is roughly where alkaline rocks plot; yellow area where subalkaline rocks plot.]] thumb|An aphanitic volcanic sand grain, with fine-grained matrix (geology)|groundmass, as seen through a [[petrographic microscope]]
Aphanites (adj. aphanitic; ) are igneous rocks that are so fine-grained that their component mineral crystals are not visible to the naked eye (in contrast to phanerites, in which the crystals are visible to the unaided eye). This geological texture results from rapid cooling in volcanic or hypabyssal (shallow subsurface) environments. As a rule, the texture of these rocks is not the same as that of volcanic glass (e.g., obsidian), with volcanic glass being non-crystalline (amorphous), and having a glass-like appearance.
Excerpted from Wikipedia’s “aphanite” article, available under the CC BY-SA 4.0 licence.