natrolite: a group of minerals of the zeolite family consisting of a hydrous silicate of sodium and aluminum
zeolite: any of a family of glassy minerals analogous to feldspar containing hydrated aluminum silicates of calcium or sodium or potassium; formed in cavities in lava flows and in plutonic rocks
sweep hand: a second hand that is mounted on the same center as the hour and minute hand and is read on the minutes