This chert sample is a unique blue-grey, silica-rich sedimentary rock collected near the village of Rhynie in the Grampian Highlands of Scotland. The Rhynie chert is a sinter, an opaline silica deposit that formed in the Early Devonian period, between 400 and 412 million years ago. Sinter is a natural deposit that forms near hot springs, coating rocks and any other objects placed in the water. What makes the Rhynie chert unique is that it contains exceptionally well-preserved fossils of some of the earliest plants and animals to colonise the land, including the remains of the oldest known, arthropods (insects).

In thin section the chert is a heterogeneous mixture of finely crystalline quartz, later porosity fillings, and many fragments of plants. There is some evidence of fossil plants in this thin section and there may even be evidence of insect fossils but we haven't found any yet.