How Does Opalized Wood Form?

Due to a series of rhyolite volcanic flows, resulting in a large basin enclosed by low hills. This basin contained a succession of lakes and forests of spruce, hemlock, birch, chestnut and even sequoia which were periodically buried by volcanic ash hundreds of feet thick. A large lake formed within the basin which deposited large amounts of diatomite, a biogenic form of silica.

As the internal structure of our plant gradually breaks down, it replaces its organic material (wood fibers) with silica and other minerals. Those minerals will crystallize over a period of a few million years. The end result is a rock that takes over our original tree’s shape and structure.