A plant that can accumulate abnormally high concentrations of heavy metal ions, such as lead, cadmium, nickel, zinc, arsenic, and aluminium. For example, alpine pennycress, Noccaea (Thlaspi) caerulescens, grows on spoil heaps and former mine workings and can contain up to 30 000 ppm of zinc compared to a typical concentration of 100 ppm in other plants. Hyperaccumulators are used in phytoremediation to extract metal contaminants from polluted land.