1/6/2023 0 Comments Deal with the bandits witchThat is a fossil sponge, many millions of years old. You may find a flint with a bubbly-textured piece sticking out. Sometimes, the piece is quite large, so the flint traps a fossil sponge, which is revealed as the outside of the flint is eroded away by natural processes. So, every flint has a piece of sponge at its heart. When the more-soluble carbonates come out of solution and form chalk, the nodules of silica get trapped in the matrix. It tends to accumulate where there is already silica, so it builds up as nodules around specks of dead sponge. As a shallow sea evaporates, the silica is the first material to come out of solution. Animals like zooplankton and sponges have a silica-based structure, which partly dissolves when they die. As the water evaporates, the dissolved solids are left behind. It's just that not very much will dissolve. It is a little-known fact that almost anything will dissolve in water, even silicates (chemicals similar to sand and glass). Flint is a particular kind of stone known as an evaporite.
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