dioriit

Diorite is a coarse-grained intrusive igneous rock with intermediate composition. It crystallizes from magma that is between felsic and mafic, and it is the intrusive counterpart to andesite. The dominant minerals are plagioclase feldspar and one or more dark mafic minerals, typically hornblende (amphibole) or pyroxene; quartz is usually scarce or absent. Accessory minerals such as biotite, magnetite, apatite, and zircon may be present.

Diorite has a phaneritic texture, with crystals large enough to be seen with the unaided eye. Its color is commonly a mottled mix of light gray to greenish gray with dark specks, giving a speckled or salt-and-pepper appearance.

Formation and occurrence: Diorite forms when andesitic magma intrudes into the crust and cools slowly underground, producing a coarse-grained rock. It occurs in plutonic bodies such as batholiths and stocks and is common in continental crust associated with subduction zones and volcanic arcs. It is frequently found in ancient mountain belts containing granitoid rocks.

Classification and relationship: In modern classifications, diorite is considered an intermediate rock. If quartz content increases, the rock may be reclassified as granodiorite. Diorite is distinguished by its relative lack of quartz and by the dominance of plagioclase feldspar over potassium feldspar.

Uses and locality: Diorite is used as dimension stone and in construction in various regions due to its durability. It has also been used historically for statuary and decorative stone in some cultures.