- Saddle Mountain, a remote and rocky ridge located in central Washington. These hills rise to 2700 feet and offer stunning views of the desert landscape and the Columbia River below. But that’s not all – the fossilized wood on these rugged hills contains a record of the area’s geological history. Petrified or opalized wood is the official gemstone of Washington, and Saddle Mountain is a treasure trove for rock enthusiasts who love agatized wood.