Complex sentence: The feldspar content ranges from oligoclase to andesite and labradorite, and is often very zonal; sanidine occurs also in some dacites, and when abundant gives rise to rocks that form transitions to the rhyolites.
Split into simpler sentences: The feldspar content ranges from oligoclase to andesite and labradorite, and is often very zoned. Sanidine occurs also in some dacites, and when abundant gives rise to rocks that form transitions to the rhyolites.