sy·e·nite 
(sīə-nīt′)
(sīə-nīt′)n.
An igneous rock composed primarily of alkali feldspar together with other minerals, such as hornblende.
[Latin Syēnītēs (lapis), (stone) of Syene, from Syēnē, Syene, an ancient city of southern Egypt, from Greek Suēnē.]
sy′e·nitic (-nĭtĭk) adj.