Flagstone is a sedimentary rock composed of feldspar and quartz. It is layered and held together by silica. It is much admired for its color variations and multiple decorative and functional uses. How you cut flagstone depends on the size and design in your project. Use a chisel to cut the flagstone if the project is small and only requires approximate sizing, such as a garden path. Use a masonry saw or water fed masonry saw for larger projects that require accurate cuts for a variety of visual effects, such as a pool deck or patio. Once you understand that this is a time-consuming and dirty job, it will work best if you know how to cut flagstone.
Use a circular saw with masonry blade to make regular cuts in the same size for small projects, such as a fireplace hearth.
Clamp the flagstone firmly to a solid surface.
Measure and clearly draw the line to cut.
Begin to saw along the line.
Do not apply pressure to the saw; just allow the weight of the saw to score the stone.The intent is not to saw through the flagstone; rather, the purpose is to create a significant score in the stone along which repeated blows with a hammer and chisel will break the stone.
Prop the stone that has been scored by the circular saw at an angle on a tool or brick along the bottom side of the flagstone parallel to the scored line.
Tap chisel with hammer sharply along the scored line until piece breaks away.