Harmotone can form as grey, white, reddish, brown or yellow. It forms hydro-thermally in volcanic cavities, ore veins and pegmatites. It is one the rarer zeolites. It was first found in 1801 in the Harz Mountains in Germany, and its name comes from the Greek words 'harmos' and 'temseis'. meaning 'a joint' and 'i cut' respectively.