Trachyte
“The rough-textured lava rock”
Igneous
Trachyte is a fine-grained volcanic rock with a distinctly rough texture that catches on your fingers when you touch it. It's the extrusive equivalent of syenite, forming from alkali-rich, silica-intermediate magmas at continental volcanoes and oceanic islands.
Composition
sanidine, plagioclase, biotite, hornblende, augite
Where Found
Phlegrean Fields (Italy), Canary Islands, Kenya Rift, Auvergne (France), Pantelleria (Italy)
Mohs Hardness
6
Fun Fact
Trachyte gets its name from the Greek 'trachys' meaning rough — run your fingers across it and the tiny aligned feldspar crystals feel like fine sandpaper.
Test Your Knowledge
Why does trachyte feel distinctly rough to the touch compared to most other volcanic rocks?
Related Specimens
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