What deposits are formed due to the activity of living organisms?

There are dozens of species of rocks in the world, the deposits of which are formed due to the activity of living organisms. For example, oil can be isolated, which is actually the remains of ancient microscopic organisms. Coal was formed, for the most part, from ancient tree ferns in cases where these plants were buried under a layer of soil after mudflows or floods of various sizes. Gypsum and limestone were formed from the shells of prehistoric molluscs and snails.