Which of the following statements is/are true? P. The silicon carbide is used as a refractory material. Q. Blast furnace is used for the smelting of lead ore. R. Calamine and casseterite are the ores of zinc.

The substances that are capable of withstanding very high temperatures without melting or becoming soft are called refractory materials like- SiC (carborundum), Al₂O₃, SiO_2, etc. Blast furnace is used for the smelting of iron, copper and lead ores. Calamine (ZnCO₃) is the ore of zinc while casseterite (SnO₂) is the ore of Sn.