You obtain some basic minerals and apply lots of heat and pressure over millions of years, then you have rock.
If you have some good base rock, generally dead live rock or porus limestone you can seed it with another peice of live rock in a rubbermaid bin or trash can. I used the same water paramaters as my main tank. Placed a heater and a power head for good circulation and let it grow, it took a little over a month for mine to culture and stunk a stunk a bit. But was cheaper than buying it cured.