Refractory clays consist of natural clay materials, mainly clays from the kaolinite group, along with fine-grained micas and quartz, and they may also contain organic matter and sulfur compounds. Refractory materials are ideal for the construction of ovens, barbecues, and chimneys, which must maintain their strength and structure at high temperatures. Depending on the application, these materials must withstand thermal shocks, be chemically inert, exhibit low thermal conductivity, and have a low coefficient of expansion.