Olivine? This is mined, which means eco-system destruction from wherever it is being mined from. It means fossil fuel inputs to mine it, process it, transport it. What's the ratio of carbon-stored to carbon-released here? Any studies on the effect of of both marine animals and the beach/dune/fringe dwellers on this?
Economical? Maybe. Actually effective? Doubt it.
People are so in love with the idea of a technical solution, because deep down they don't want to give up their SUVs, their large families, their expensive gadgets and cheap food. It ain't never gonna work that way.
If people were serious about solving the climate problem, they would have smaller families, drive smaller cars, cut-out air travel, stop buying plastic shit they don't need, stop upgrading their phone every year ...
... but I'm not seeing many people doing it. Pretty much nobody in fact.