It is also used in cement, in gemstones, as an optical opacifier in paper, and a strengthening agent in graphite composite fishing rods and golf clubs. pigment is chemically inert, resists fading in sunlight, and is very opaque: it imparts a pure and brilliant white color to the brown or grey chemicals that form the majority of household plastics. In nature, this compound is found in the minerals anatase, brookite, and rutile. Paint made with titanium dioxide does well in severe temperatures and marine environments. Pure titanium dioxide has a very high index of refraction and an optical dispersion higher than diamond. In addition to being a very important pigment, titanium dioxide is also used in sunscreens. Aerospace and marine Because titanium alloys have high tensile strength to density ratio, high corrosion resistance, fatigue resistance, high crack resistance, and ability to withstand moderately high temperatures without creeping, they are used in aircraft, armor plating, naval ships, spacecraft, and missiles. For these applications, titanium is alloyed with aluminium, zirconium, nickel, vanadium, and other elements to manufacture a variety of components including critical structural parts, fire walls, landing gear, exhaust ducts (helicopters), and hydraulic systems. In fact, about two thirds of all titanium metal produced is used in aircraft engines and frames. The titanium 6AL-4V alloy accounts for almost 50% of all alloys used in aircraft applications. The Lockheed A-12 and its development the SR-71 "Blackbird" were two of the first aircraft frames where titanium was used, paving the way for much wider use in modern military and commercial aircraft. A large amount of titanium mill products are used in the production of many aircraft, such as (following values are amount of raw mill products used ... only a fraction of this ends up in the finished aircraft): 116 metric tons are used in the Boeing 787, 77 in the Airbus A380, 59 in the Boeing 777, 45 in the Boeing 747, 18 in the Boeing 737, 32 in the Airbus A340, 18 in the Airbus A330, and 12 in the Airbus A320. In aero engine applications, titanium is used for rotors, compressor blades, hydraulic system components, and nacelles. An early use in jet engines was for the Orenda Iroquois in the 1950s. Because titanium is resistant to corrosion by sea water, it is used to make propeller shafts, rigging, and heat exchangers in desalination plants; heater-chillers for salt water aquariums, fishing