Titanium

Titanium (as an alloy) is used for sunglasses because it is as strong as steel, but weighs only about half as much; it has the highest strength-to-weight ratio of any metal. Titanium is also easy to fabricate with and has excellent corrosion resistance. Titanium was discovered in 1791, although pure titanium was not made until 1910. Titanium is the ninth most abundant element in the earth’s crust. Because of its strength and corrosion resistance it is used in the aerospace and marine industries, but it is also used where you wouldn’t think, like in toothpaste, in paints and horseshoes.