igneous
Syenite
Syenite (Phaneritic Igneous Rock)
Hardness: 6-6.5 on Mohs scale; Color: Variable, often grey, pink, or brownish with dark spots; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Perfect in two directions (due to feldspar); Specific gravity: 2.6-2.8
- Hardness
- 6-6
- Color
- Variable, often grey, pink, or brownish with dark spots
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-6.5 on Mohs scale; Color: Variable, often grey, pink, or brownish with dark spots; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Perfect in two directions (due to feldspar); Specific gravity: 2.6-2.8
Formation & geological history
Formed through the slow cooling of alkali-rich magma deep within the Earth's crust, often associated with continental rifting or subduction zones. Most specimens are Proterozoic to Cenozoic in age.
Uses & applications
Used as a dimension stone for building facades and countertops, as decorative aggregate in landscaping, and occasionally as a source of aluminum or rare earth elements.
Geological facts
Syenite is often mistaken for granite but is distinguished by its lack of or very low quartz content (less than 5%). It is named after Syene in Egypt, though the rocks originally found there were actually granites.
Field identification & locations
Identify in the field by its coarse-grained texture and the visible absence of quartz crystals. It typically contains high amounts of alkali feldspar and darker minerals like hornblende or mica. Highly common in alkaline igneous provinces like those in Norway, Canada, and Arkansas, USA.
