Clay is principally used in Switzerland as raw material for bricks. Clays are fine-grained products of weathering of other types of rock. Basically, a difference is made between transported sediments and «in situ», i.e. in place, products of weathering. Raw material properties and the formation of the deposits are influenced by the origin of the materials and the transport mechanisms, by the sedimentation environment as well as by chemical transformations and the degree of solidification.
Switzerland is a country rich in raw materials for the production of bricks. In addition to archaeological artefacts, this is evidenced by numerous prehistoric pits for clay extraction and historical localities. At the beginning of the 20th century, over 300 small brickyards were supplied in raw materials by as many clay pits. The majority of the pits were in the Plateau region, the Jura and in the peripheral areas, while only a few deposits were found in the Pre-Alps and in the large Alpine valleys and in the canton of Ticino (Pliocene marl and Pleistocene loam). Small production centres, as well as the first mechanised brickyards, mainly used the many available deposits of more or less strongly decalcified, plastic surface clay. The limited availability of these materials and the tendency in this century to replace old brickyards with bigger, more efficient plants forced the industry to find new sources of raw materials. Thus an increased amount of solid rock, such as marl or clay schists were used, which represent at present four fifths of the annual extracted volume. The remaining 34 brickyards still in service until the end of 2000 covered their needs for raw materials from 58 pits.

Raw material reserves
The annual amount of extracted material from the clay pits varies between 100 and 100,000 cubic metres, with a mean value of about 25,000 cubic metres. In the year 1991, a total of approximately 1.4 million cubic metres of brick raw material was extracted. The assured raw material reserves are about 35 million cubic metres of material (solid volume), which will suffice to cover Swiss needs completely for approximately 35-40 years. In addition, about 70 million cubic metres of estimated reserves exist in the vicinity of currently used pits. Thus, Switzerland still has an enormous raw material potential, especially in molassic marl and opalinus clay.