1. Dolmite bricks

• Preparation: Dolmite bricks are made by mixing calcined dolmite (CaO+MgO mixture in equimolecular preparations) with silicate binder. They are fired at 1500 °C for about 24 hours
• Properties: Dolmite bricks possess less strength, more softness and porosity, greater shrinkage and high hygroscopicity than magnasite bricks. However, they can withstand a load of 3.5 kg/cm2 at 1650 °C. They are also not very resistant to thermal shocks.
• Uses: Dolmite is rarely used as a direct refractory, but it is useful as repair material.
• Stabilized dolmite bricks are, however used for basic electric furnace linings.
• Bessemer converters, open-hearth furnaces, ladle-linings etc. and as a cheap substitute for magnesite bricks.

2. Silicon carbide:

• Preparation: It is a bluish-black crystalline artificial mineral with hardness between corundum and diamond.

• It is made by subjecting a mixture of silica and carbon (coke or coal) to high temperature (1650-2200 °C) in an electric furnace

• It is very hard, chemically unreactive, can withstand the action of high temperature without damage, but it is not tough and is somewhat brittle. It is mainly used in cutting-wheels, abrasive papers and clothes. It is extensively used for grinding of materials of low tensile strengths like cast iron, brass, bronze and many more.