A slice of very deep time. Stromatolites are layered structures built up over centuries by mats of microbes that trapped and bound sediment a thin film at a time, and they count among the oldest visible records of life on earth, going back billions of years. Living examples still grow in a few places, which is part of what makes them extraordinary: a life form that has barely changed since before complex life existed.

The polished face makes that slow build-up readable, almost like grain in wood but on a geological clock. It came to us at auction from a regional Victorian museum collection, dispersed when the museum closed, which is the kind of afterlife these objects tend to have. We don't tie it to a single locality.