Miocene Plateau Basalt is a 13 to 16 million year formation that consists of 50,000 square miles covering most of central and eastern Washington and in places a mile deep. The massive lava flows are likely the result of slide faults along the cascade range of volcanoes opening large rifts creating flows that poured into the basin creating the Columbia Plateau. At the end of the last Ice age about 16000 years ago the breach of the Ice Dam that created lake Missoula was breached and in one of North Americas most dramatic geologic events the Spokane flood scoured the land and revealed the basalt formations as we see them today.
The Blue and Gray Basalt Quarries are from a relatively recent (in geologic time tables) high cascade lava flow. This is some of our regions youngest stone. The stones we carry can’t be thermal finished as our Black Basalt products. They can however be sandblasted, polished, and antique finished. The Blue Basalts offer larger natural slab sizes while the Gray Basalt offers a hint of purple and pink.