Browse Items (156 total)

(unnumbered) Compression fossils most often form in sedimentary rocks called shales which form in the bottom of lake or sea beds. The same fossil can be seen in both the part and counterpart but different features are often preserved on both sides.…

(DSM #M76 and #M172) These interal casts show the shape of the inside of a cavity such as a shell or brain. When you have an imprint of the outside of an organism it is calleda mold.

(DSM #SD7) Dendrites are iron or manganese oxide mineral growths that occur in a rock after deposition.

(DSM #SD8) Geodes are crystals that form to fill a void. The outer portion of the stone is usually non-descript and plain but the crystals show themselves when the rock is hit with a hammer.

(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…

(DSM #SD13) Septarian concretions form in cavities where the outer rock is cracked and angular. Minerals fill the cracks and preserve their shape.