Sphalerite is a zinc-sulfide with varying content of iron, chemical formula (ZnFe)S. When low in iron its crystals have a yellow to brown luster. With more iron it is an opaque, dark metallic-grey, as in this sample, and then sometimes referred to as marmite.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 main body of this sample is quartz in a habitat of small prismatic crystals. Sample is from Madan in Bulgaria, actual width is 27 cm.