Lewis & Short

Syēnē, ēs, f., = Συήνη, a town at the southern extremity of Upper Egypt, now Essouan, Plin. 2, 73, 75, § 183 sqq.; Ov. P. 1, 5, 79; Mel. 1, 9, 9; Luc. 2, 587; 10, 234; Mart. 9, 36, 7.
Meton., the granite of Syene, Syenite, Stat. S. 4, 2, 27.
Hence, Syē-nītes, ae, adj. m., of or belonging to Syene, Syenite: Phorbas, Ov. M. 5, 74: lapis, a kind of red granite, Syenite, Plin. 36, 8, 13, § 63.
As subst.: Syēnītae, ārum, m., the inhabitants of Syene, the Syenites, Plin. 6, 29, 35, § 178.