Choose a rock-cutting blade. The quality of the blade chosen depends upon the density of the rock and how much cutting you are going to do. Diamond-tipped blades are commonly used to cut rock. Most are abrasive but not sharp.
Unscrew the bolt on the circular saw that holds the blade in place. This is done with either a hex key that came with the saw or an adjustable wrench.
Lift up the blade guard to expose the blade.
Remove the standard blade from the saw with gloved hands.
Slide the new rock-cutting blade onto the saw. There should be an arrow on the blade and one on the blade guard. Both arrows must point in the same direction.
Push the blade guard back down over the blade.
Tighten the bolt to securely fasten the blade to the saw.