Sponge

Flask-shaped flint

Flints are made from silica that originally derived from sponges living in the chalk sea. The sponges are made up of millions of minute needles of silica locked together to form this simple animal. When the sponges died, the needles were scattered on the sea bed and buried in the sediment.

Later, ground water dissolved the silica and carried it in solution down through the rock layers. That silica-rich water gathered in cavities and spaces such as hollow burrows and other sponge bodies where the silica recrystallized, forming flint. That’s why flints are often long, thin and branching, where they filled burrows, or flask-shaped (like this specimen) where they formed around a sponge.

Find out more on the sponges page.

Common name

Sponge

Scientific name

Siphonia

Type

Other


Strata

Chalk

Time period

Upper Cretaceous

Age

85 million years

Where found

Moigne Combe, near Crossways

Found by

Mrs M F Giles Puller

Museum

Dorset County Museum, Dorchester

Accession number

DCM.G.09050