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
water softener: a substance (such as sodium chloride) that lessens the hardness of water by replacing calcium and magnesium ions with sodium ions and so gives the water more efficient sudsing power
holy roman empire: a political entity in Europe that began with the papal coronation of Otto I as the first emperor in 962 and lasted until 1806 when it was dissolved by Napoleon