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Hesperus Mountain, showing wedges and sheets of trachyte intruded into the shales, from the laccolith of Mt. Moss.

Hesperus Mountain

Hesperus Mountain, showing wedges and sheets of trachyte intruded into the shales, from the laccolith…

Trachyte is an igneous, volcanic rock with an aphanitic to porphyritic texture.

Trachyte-phonolite

Trachyte is an igneous, volcanic rock with an aphanitic to porphyritic texture.