Preseli Bluestone is a dolerite rock found in the Preseli Hills of Wales, United Kingdom. It is a type of igneous rock, primarily composed of plagioclase feldspar, pyroxene, and quartz, giving it a distinctive blue-gray color with white and green speckles. This stone is most famous for being used in the construction of Stonehenge, where its origins date back to around 3000 BCE. It has a Mohs hardness of approximately 6 to 7, making it relatively durable. Preseli Bluestone is valued for both its historical significance and its unique speckled appearance.