Sanidine trachyte is an igneous rock with an aphanitic to porphyritic texture. Chemically it is the volcanic equivalent of syenite. It contains up 65 % silica which rarely appears as quartz crystals. The dominant feldspar is sanidine (potassium feldspar). Trachyte can show a banded or streaky flow structure. The flow is picked out in thin section by aligned tabular phenocrysts & sanidine laths. The rock often contains minute irregular steam cavities which give specimens a rough texture & hence the name.