1. Many Bedded cherts are made up of the remains of siliceous organisms such as diatoms, radiolarians, or sponge spicules

2. Cherts often have an “indirect” biogenic origin as they result from re-precipitation of dissolved opal-A shells derived from microorganisms such as diatoms (diatomite , diatomaceous Cherts, see also entry “ Diatoms ”) and radiolarians (radiolarite , see also entry “ Protozoa (Heterotroph, Eukaryotic) ”).