This mineral makes up adamantine spar.
Titanium inclusions in this mineral can form a "silk" pattern. This mineral names and is the basis for the structure of ilmenite. Star stones are most commonly composed of this mineral. The creation of this mineral is the primary use of the Verneuil process. When this mineral is mixed with magnetite or other iron compounds, it forms (*) emery. This mineral makes up adamantine spar. One form of this mineral can have a color known as pigeon's blood. The basic unit of this mineral consists of three oxygens and two aluminium atoms. For 10 points, name this mineral that is a 9 on the Mohs scale and forms the basis of sapphires and rubies.
Titanium inclusions in this mineral can form a "silk" pattern.
corundum [prompt on Al2O3; prompt on aluminum oxide]