Trachyte is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and fine-grained, with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and alkali metals.
It is the volcanic equivalent of syenite.Trachyte is common wherever alkali magma is erupted, including in late stages of volcanism of ocean islands and in continental rift valleys and above mantle plumes. Trachyte has also been found in Gale crater on Mars.
Trachyte has been used as decorative building stone and was extensively used as dimension stone in the Roman Empire and the Republic of Venice.
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