Calcium Carbonate concretions
(DSM #SD11 and #SD12) Concretions come in all sizes and are very often mistaken for fossils because of their intricate and strange shapes. They form when a grain of sediment or organism acts as a nucleus for minerals to precipitate and grow. Some concretions contain fossils but many do not.
Pseudofossil - Septarian nodule
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“Pseudofossil - Concretion,” Mississippi State University Libraries, accessed June 30, 2022, http://msstate-exhibits.libraryhost.com/items/show/1664.