Rhyolite is a relatively rare volcanic rock with the same mineral makeup as granite. While it most commonly occurs with obsidian, rhyolite also serves as the parent rock for the formation of Oregon Opal. Because rhyolitic lava is so thick, it seldom makes it to Earth’s surface, but when it does, it piles over volcanic vents without flowing away, forming a dome. Such a dome is currently forming within the crater of Mount St. Helens in SW Washington. Metaphysically, rhyolite is said to represent change, creativity, and progress.