Which of the following is not an example of organically formed sedimentary rocks?

Question

The rocks formed from the remains of living organisms such as corals or shellfish, whose fleshy parts have been decomposed, leaving behind the hard shells. The most common rocks formed in this way are the calcareous type. They include limestones and chalk. The carbonaceous rocks are also formed organically but from vegetative matter-swamps and forests. Its examples are peat, lignite or coal.
Gypsum or calcium sulphate is chemically formed sedimentary rock. It is obtained from the evaporation of salt lakes such as the Dead Sea.

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Gypsum

The rocks formed from the remains of living organisms such as corals or shellfish, whose fleshy parts have been decomposed, leaving behind the hard shells. The most common rocks formed in this way are the calcareous type. They include limestones and chalk. The carbonaceous rocks are also formed organically but from vegetative matter-swamps and forests. Its examples are peat, lignite or coal.
Gypsum or calcium sulphate is chemically formed sedimentary rock. It is obtained from the evaporation of salt lakes such as the Dead Sea.

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