Natural Stromatolite Gemstone Lot, Mixed Shape 20 to 40mm – Fossilized Ancient Life Cabochon

Both, actually. Living stromatolites still form in a handful of extreme environments today, most famously in Shark Bay, Australia, but the material used for gemstone cabochons is fossilized rock, often billions of years old, mined from ancient formations rather than harvested from living colonies.

Each layer reflects a different period of microbial growth and mineral deposition, so variations in water chemistry, sediment, or growth rate over time show up as different colored bands. That's also why the pattern reads almost like tree rings, a genuine record of change over a very long timescale.

They're related in look but not identical. Kambaba jasper is technically a variety of stromatolite that formed in specific ancient volcanic environments and often shows a distinct green tone from included minerals, while general stromatolite material shows a wider range of colors depending on where it formed.

It varies by source material, but fossil stromatolite used in jewelry commonly dates from hundreds of millions to over a billion years old, depending on the deposit it came from. Exact dating usually isn't provided at the point of sale, but the geological formations these stones come from are consistently ancient.

Age doesn't affect durability the way people sometimes assume, the fossilization process essentially turned the material to solid rock, generally rating in a moderate hardness range similar to other banded stones like jasper. It holds up well in pendants and rings, though as with any patterned stone, avoiding hard impacts keeps the surface looking its best.