Chalk is also calcium carbonate. Can you use powdered chalk in the same way as lime? Presumably there is a structural difference between the two that may affect the way it is absorbed.  Has anyone tried it?

I live on very chalky soil and have a ready supply of great lumps of it lying on every ploughed field.  Would it need to be baked (pasteurised) before using it? It tends not to pick up mould or organic matter in the ground but might still harbour dormant spores?