The mined media is likely Calcite. It does not take that much more co2 to melt if you let your reactor run 24/7 and don't try and "control" it with a pH probe. If you are dumping co2 with a probe/regulator, then it will take more co2 and more will escape into the tank. With any type of media, your tank pH will be higher if you have no extra co2 leaving the reactor, so just tune it well by hand and you will be fine.