Clinker is the intermediate product in cement manufacturing. It is obtained by burning an intimate mixture of carefully proportioned raw materials - typically limestone and clay - at very high temperatures in a kiln.
 
In order to obtain the various types of cement, as specified in EN 197-1, clinker is intergrounded with a limited percentage of gypsum and with other main constituents i.e. granulated blastfurnace slag, pozzolanic materials, fly ashes, burnt shales, limestone and silica fume.

Clinker, if stored in dry conditions, can be kept for several months with no appreciable quality losses. This is the reason why clinker is easily handled by ordinary mineral handling equipment and traded internationally in large quantities.