Most are engaged in the extraction of kaolin, fluorspar and Agalmatolite and Kaolin is exported. Insulating refractories include calcium silicate materials, kaolin, and zirconia. Rocks that are rich in kaolinite are known as kaolin or china clay. The common clay minerals are montmorillonite or smectite, illite, and kaolinite or kaolin. Hard-paste now chiefly refers to formulations prepared from mixtures of kaolin, feldspar and quartz. Victoria also produces limited amounts of gypsum and kaolin. Other natural resources include kaolin, salt, phosphate, and limestone. The underground resources include gold, zinc, copper, fluorspar, limestone, granite, and kaolin. Clay is the primary ingredient of kaolin. Lesser amounts of copper, lead, molybdenum, gold, silver, kaolin, and fluorite also were mined. White from kaolin or mica was used occasionally. These include minerals such as coal, limestone, sillimanite, Kaolin and granite among others. In nature it is frequently altered to zeolites (especially natrolite), sodalite, kaolin, or compact muscovite. This porcelain is made of hard paste that mainly consists of kaolin, or china clay. They are a major component of kaolin and other clay minerals.