Tantalite

Tantalum: Swedish scientist Anders Ekberg discovered tantalum in 1802, but it was confused with niobium, because of their twinned properties, until 1864, when it was recognized as a separate element. Tantalum is a dark blue-gray, dense, ductile, very hard, and easily fabricated metal. It is highly conductive to heat and electricity and renowned for its resistance to acidic corrosion. These special properties determine their primary uses and make niobium and tantalum indispensable. Tantalum can both store and release energy, which allows electronic parts be exceptionally small. Image credit: By Photograph by Andrew Silver - http://libraryphoto.cr.usgs.gov/htmllib/btch571/btch571j/btch571z/byu01…, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7598843