How can I make concrete look like natural stone?

Hello everybody, I am Roz and have been using Lumber jocks for some time. This is my first foray into Home Refurbishes.
My wife and I are restoring an 1860’s home and I want to create a brick paved patio in the small area between the house and my shop. In this patio I would like to set a mill stone. I have not found one that I felt I could afford.

My idea is to make a stone from concrete. What I don’t know is how to finish the concrete to make it look like natural stone and how best to make the required groves in the surface. I would like the concrete to resemble granite, sand stone or other natural material.

Do any of you have recommendations?