Much appreciated by our ancestors for its practical properties, flint is known for its extraordinary robustness. Polished, it becomes shiny like glass. Mainly composed out of silica, this stone often holds fossilized organic deposits and limestone, offering a surprising range of colors and patterns. This happens during its formation at the bottom of the oceans, when the flint stone “colonizes” the surrounding limestone. The white gangue surrounding the lump is called “cortex”, and is composed of the organic deposit that were pushed back to the outside during the growth of the lump.