diorite

di·o·rite

noun \ˈdī-ə-ˌrīt\

Definition of DIORITE

: a granular crystalline igneous rock commonly of acid plagioclase and hornblende, pyroxene, or biotite

— di·o·rit·ic \ˌdī-ə-ˈri-tik\ adjective

Origin of DIORITE

French, irregular from Greek diorizein to distinguish, from dia- + horizein to define — more at horizon

First Known Use: 1826

diorite

noun    (Concise Encyclopedia)

Medium- to coarse-grained igneous rock that commonly is composed of about two-thirds plagioclase feldspar and one-third dark-coloured minerals, such as hornblende or biotite. Diorite has about the same structural properties as granite but, perhaps because of its darker colour and more limited supply, is rarely used as an ornamental building material. It is one of the dark gray stones that is sold commercially as “black granite.”