Banded flint

How flint forms

Banded (or striped) flints are something of a mystery as no-one is quite sure how they form. The flint itself originated from the spines of sponges that became buried in the ooze at the bottom of the chalk sea. Later, ground water percolating through the chalk dissolved the spines and carried the silica in solution down through the rock. Holes left by burrowing animals and sponges were filled with this water and the silica crystalized out to form flint. That is why flints are typically round in section and branching as they form inside burrows of that shape, or they contain sponges.

Find out more on the rocks and pseudofossils page.

Common name

Banded flint

Type

Rocks and Pseudofossils


Strata

Chalk

Time period

Upper Cretaceous

Age

85 million years

Where found

Dorchester

Found by

Unknown

Museum

Dorset County Museum, Dorchester

Accession number

DCM.G.10468