phanerittinen

Phanerittinen, or phaneritic in English, is a texture term in geology used to describe igneous rocks whose crystals are coarse-grained and visible to the naked eye. The name comes from the Greek phaneros, meaning visible. This texture reflects relatively slow cooling of magma, typically deep within the crust, which allows individual minerals to grow to noticeable sizes before solidification.

Phaneritic rocks are usually intrusive (plutonic) in origin, forming in settings such as batholiths, stocks, and magma chambers. The crystals are generally interlocking, giving the rock a uniform, coarse-grained appearance. The mineral assemblage can range from felsic to mafic, with common examples including granite, granodiorite, and diorite (felsic to intermediate) as well as gabbro and diabase (mafic). In felsic phanerites, light-colored minerals such as potassium feldspar, plagioclase, and quartz dominate, while mafic phanerites contain more ferromagnesian minerals like hornblende or pyroxene and appear darker.

Phaneritic texture is contrasted with aphanitic texture, where crystals are too small to see without magnification, indicating rapid cooling often associated with volcanic (extrusive) rocks. Some rocks may exhibit a porphyritic texture, featuring large crystals (phenocrysts) embedded in a finer-grained groundmass; a rock can be both porphyritic and phaneritic if its groundmass is coarse-grained.

In Finnish geology, the term phanerittinen is used similarly to describe this coarse-grained, visible-crystal texture, which is a key criterion in classifying igneous rocks and understanding their cooling history.