I used rockdust this year Next door has not been gardened for 10 years, the veg patch was in a poor state , and i read about research being done all over the world about remineralistion. It improves yield everywhere except the West Australian wheat belt. They are on practically pure sand with no worms. Where it is mixed with fibrous matter such as FYM and worms work it, it seems to work very well. Certainly this year we had the best yields ever, taking account of it being a good year, but I have been here over 20 years, and it was still the best. I put a shovel full on per square yard. I bought it in a tonne bag , delivered on a pallet. It is about a fifth of the price per kg, than buying small bags from B&Q. Also I use calcified seaweed (maerl) instead of lime, for any patch that needs liming. I am trying to get the whole soil system into good productive soil. Sweet peas seem to benefit too.