Phytomining, sometimes called agromining, is the concept of extracting heavy metals from the soil using plants. Specifically, phytomining is for the purpose of economic gain. The approach exploits the existence of hyperaccumulators, proteins or compounds secreted by plants to bind certain metal ions.  These extracted ores are called bio-ores.   The approach has little practical value ("its commercial viability is limited") because it is slow and inefficient.