Grinding wheels or other bonded grindstones that have two main components:

Alumina is the most commonly used abrasive in grinding wheels.Velcro Sanding Disc  It is usually chosen to grind carbon steel, alloy steel, high speed steel, malleable cast iron, wrought iron, bronze and similar metals.

Zirconia Alumina is another family of abrasives, made from blends of alumina and zirconia in varying proportions. This combination produces a strong, durable abrasive that excels in rough grinding applications.

Silicon carbide is another abrasive used for grinding grey iron, chilled iron, brass, soft bronze and aluminium, as well as stone, rubber and other non-ferrous metals.