Stone Type: Igneous
‘Igneous’ is a catch-all term to describe rocks formed when molten magma cools and solidifies. Intrusive igneous rocks form below the Earth’s surface, usually resulting in relatively coarse-grained stones like granite or diorite. Extrusive igneous rocks form when magma reaches the surface and cools and solidifies rapidly. These are also called ‘volcanic’ rocks. Volcanic rocks are often finer-grained and suitable for flaking, such as basalt, rhyolite, or obsidian.