But despite its abundance, it’s only recently that civilization has been able to use titanium as a metal (titanium dioxide has been in use somewhat longer as a paint pigment). Because titanium so readily bonds with oxygen and other elements, it doesn’t occur at all in metallic form in nature. One engineer described titanium as a “streetwalker,” because it will pick up anything and everything. While copper has been used by civilization since 7000 BC, and iron since around 3000 BC, titanium wasn’t discovered

Source: The Story of Titanium – by Brian Potter