Red and green stones, angular and interspersed with calcite veins - the radiolarites bring colour into play on the grey gravel banks!
To get to the place where this rock was formed, you would have to use a diving robot nowadays. In the deep sea areas (3,500 - 5,000 metres) of the primeval Pacific, it is 150 million years originated from radiolarian skeletons.

Radiolarians are unicellular organisms. Their inner skeleton consists of silica crystals which, unlike calcareous compounds, do not dissolve even at this depth in the sea.

The radiolarite is a hard rock. In the Stone Age it was used to make tools such as arrowheads.