Snakeskin Agate nodule 17 g

Snakeskin Agate nodule from Rome, eastern Oregon.

These small siliceous concretions are interpreted to be of microbial origin as discussed in the book “Biominerals“, page 321 (Campos-Venuti, 2022). The internal structure is pure translucent chalcedony without any clue on they origin, but the skin with pinnacles and furrows is undoubtely a bioconstruction, very similar to many stromatolites. So this is a real fossil microbialite. Colloidal silica precipitate inside the biofilm in the form of a small lump. Then the lumps agglomerate together slowly forming the nodule.