Very interesting article. It's amazing how many useful things are discovered by accident.
I'm a little confused about how the peridotite could react with CO2 underwater. Does the action require air to occur or does the rock just react with CO2 in the air? Anyone care to clarify?
I would guess that dissoved CO2 in the water reacts with the rocks to form carbonate (my guess it is magnesium carbonate). Then the less than saturated water absorb CO2 from the air at the water/air interface.
Very interesting and promising approach of CO2 control, favourable over CSS. Just as a side note, an earlier mention of this idea (apparently Kelemen and Matter apologized for the credit omission), roofs in Amsterdam have recently been fitted roofing that incorporates CO2 absorbing minerals.