Agreed with above. Just be careful...a lot of companies selling "pre-cured" just to confuse you more. Anyway, whatever type of rock you get, place in rubbermaid with powerhead and heater, do frequent water changes and when it smells clean "like the sea" it's okay to put in your tank.
If your tank is already established, try not to put to much rock in at once, it may cause a mini-cycle.
HTH Jim