These galena spinel twins are from the Madan Ore Field in the Rhodope Mountains, Smolyan Oblast, Bulgaria. This area contains several ore bodies that have been mined for hundreds of years. Dozens of mines were worked for the recovery of lead and zinc. It contains 75 different mineral species including galena. which is a sulfide that contains the elements Pb and S. This is an excellent double sided piece consisting of a complex cluster of galena crystals displaying multiple spinel twinning. They have a silver-grey color and a metallic luster. This piece measures approximately 1 13/16 x 1 5/16 x 3/4 inches or 46 x 33 x 19 mm.