Noun
Orig., a rock composed of quartz, hornblende, and feldspar, anciently quarried at Syene, in Upper Egypt, and now called granite.
A granular, crystalline, ingeous rock composed of orthoclase and hornblende, the latter often replaced or accompanied by pyroxene or mica. Syenite sometimes contains nephelite (elaeolite) or leucite, and is then called nephelite (elaeolite) syenite or leucite syenite.
Source: Webster's dictionaryComposition of syenites The feldspar component of syenite is predominantly alkaline in character (usually orthoclase ). Source: Internet
The quartz-syenites and nordmarkites may be interposed between granite and syenite, the tonalites and adamellites between granite and diorite, the monzoaites between syenite and diorite, norites and hyperites between diorite and gabbro, and so on. Source: Internet
The Malvern Hills, which is on the border between the counties of Herefordshire and Worcestershire United Kingdom also formed of syenite. Source: Internet