Igneous and Metamorphic Rock Textures
Allotriomorphic-granular (gabbroic) texture is a feature of phaneritic rocks in which all of the minerals have anhedral shapes; it is characteristic of some mafic and ultramafic rocks, such as dunite and pyroxenite.
Porphyritic texture: rocks in which larger grains are contained in a finer grained matrix. May occur in either intrusive or extrusive rocks, but it is most common in extrusive rocks such as basalt, andesite, dacite, and rhyolite.
Pyroclastic texture: produced by explosive volcanism, broken clasts of mineral, lithic clasts, and glass shards are common. The clasts may be either sorted or unsorted. Common in tuffs.
Intergranular texture: Plagioclase laths with interstitial pyroxene grains that are smaller than the plagioclase; commonly found in basalts.
Intersertal texture: Small feldspars with glass or altered glass interstitial to the feldspars; common texture of basalts.
Ophitic texture: Pyroxene grains partially or completely surround plagioclase laths; common texture of gabbros and basalts.
Trachytic texture: Subparallel feldspars formed during flow in volcanic rocks.
Spinifex texture: Interlacing olivine or pyroxene, a texture formed by quenching in komatiites.
Some Metamorphic Textures
Phyllitic texture: Strong foliation in fine-grained metamorphic rocks.
Granoblastic texture: Massive, unfoliated, equigranular texture in metamorphic rocks.
texture: Metamorphic texture consisting of large grains in a finer