Galena, also known as galenite and lead-glance is a natural mineral composed of lead sulfide (PbS). It is the most important ore of lead and deposits are found worldwide. It occurs as dull grey to silvery grey cubes or octahedral crystals, sometimes with skeletal surface. Its crystal symmetry is isometric hexoctahedral. The yellow brown encrustations on the crystal rims are calcite. This specimen is from a mining area near Madan, Bulgaria, actual width is 21 cm.