igneus

Igneus is a Latin adjective meaning “of fire” or “fiery.” In classical Latin it describes things related to fire, heat, or volcanic origin. The word derives from ignis, fire, and forms a masculine nominative igneus, with feminine ignea and neuter igneum. In English, the cognate term ignEous is formed from igneus through Latin and Romance-language pathways.

In geology, the English adjective igneous—ultimately from igneus—applies to rocks formed by the cooling and solidification of molten material. These rocks crystallize from magma beneath the surface (plutonic or intrusive) or from lava erupted onto the surface (volcanic or extrusive). Igneous rocks are categorized by texture (phaneritic, aphanitic, porphyritic) and composition (felsic to ultramafic). Common examples include granite (felsic plutonic), diorite (intermediate plutonic), basalt (mafic volcanic), rhyolite (felsic volcanic), and obsidian (glassy). The terminology helps contrast them with sedimentary and metamorphic rocks.

Historically, igneus has occurred in Latin texts to describe fiery colors, phenomena, or origins, and it contributed to the formation of the modern scientific term igneous. Its influence extends into Modern Romance languages, where descendants such as French igneux and Spanish ígneo carry related meanings related to fire or igneous origin. In summary, igneus sits at the linguistic root of a key geological category and captures the classical association between fire and molten rock.