What is a mineral usually of a reddish brown color, and brilliant metallic adamantine luster, occurring in tetragonal crystals. In composition it is titanium dioxide, like octahedrite and brooklite called?

rutile — A mineral usually of a reddish brown color, and brilliant metallic adamantine luster, occurring in tetragonal crystals. In composition it is titanium dioxide, like octahedrite and brooklite. (Webster's 1913.)

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