The aim of the paper is to consider sapropel classification, formation, properties and possibilities of use. Theoretical framework of the research is established by analysing literature on sapropel. Sediments accumulate during the lake existence period and they are formed from the remains of organisms living in the lake and its surroundings, and mineral material supplied to the lake from the catchment area and atmosphere. In the freshwater bodies located in the temperate forested areas, usually sediments with high organic matter content (over 15%) are formed from aquatic plants, mainly fresh water algae, plankton and benthic organisms and transformed under influence of bacteria, and mixed with mineral components. Sapropel has a finely dispersed and plastic structure; the colour – from light pink to dark brown. Usually sapropel is divided into four big types: organic, silicate, carbonatic and mixed. Each sapropel type is subdivided. Latvia has 2256 lakes with a total area of 1001 km2 or 1.5% of the country. The total area of mires is 6401 km2 or 9.9% of Latvia. Most lakes and bogs contain sapropel deposits. The State Geology Office of Latvia states that there are more than 750 million m3 of lake sapropel resources and about 1.5 billion m3 of sapropel reserves. There are about 2 billion m3 of joint sapropel resources in Latvia. It is suggested that sapropel can be used in various fields. In some countries, for instance, in Russia, Byelorussia and Ukraine, sapropel is used in balneology, livestock farming, agriculture, cosmetology and other fields. However, nowadays the products made on the basis of peat are more popular; therefore, the studies of the organic sediments of lakes are rare.