Syenite is a plutonic rock consisting chiefly of potassium feldspar with a subordinate amount of plagioclase feldspar and little or no quartz. (more below)
The dark, mafic minerals in syenite tend to be amphibole minerals like hornblende. See its relation to the other plutonic rocks in the QAP classification diagram.
Being a plutonic rock, syenite has large crystals from its slow underground cooling. An extrusive rock of the same composition as syenite is called trachyte.
Syenite is an ancient name derived from the city of Syene (now Aswan) in Egypt, where a distinctive local stone was used for many of the monuments there.
However, the stone of Syene is not a syenite, but rather a dark granite or granodiorite with conspicuous reddish feldspar phenocrysts.
The dark, mafic minerals in syenite tend to be amphibole minerals like hornblende. See its relation to the other plutonic rocks in the QAP classification diagram.
Being a plutonic rock, syenite has large crystals from its slow underground cooling. An extrusive rock of the same composition as syenite is called trachyte.
Syenite is an ancient name derived from the city of Syene (now Aswan) in Egypt, where a distinctive local stone was used for many of the monuments there.
However, the stone of Syene is not a syenite, but rather a dark granite or granodiorite with conspicuous reddish feldspar phenocrysts.