"cured" simply means that any dead material has been broken down and a substantial amount of bacterial life has formed as a result of dealing with the nitrogen cycle. If you are buying lr
from the lfs
, and it is in an established system, and has been there for some time, it is cured.
Base rock is often rock that has been bleached and is void of any life. No curing is required. You can put that marco rock right in your tank by the handful and you will not see a spike of any kind, although rinsing is always a good idea.