Stainles steel and titanium choker, c 1976.
© Science Museum / Science & Society Picture Library
Detail of a choker made by Lexi Dick, and first exhibited at the Goldsmith's Company, London. The blue effect is obtained by heating the titanium which develops a translucent surface film. Although first discovered by W Gregor (1761-1817) in 1791, titanium was not commercially manufactured until 1948. It is extremely useful in alloys, as the metal is as strong as steel, but 45 % lighter. This combination of lightnes and strength, together with high resistance to corrosion, makes titanium alloys very important to the aerospace industry. Titanium makes up 0.6 % of the Earth's crust.