Basalt dust worth it?

I read about rock dust and paramagnetic rock dust. The next basalt quarry is about 80 km from here and we could either order a truckload or get a trailerload, I haven't asked the price yet. Is it worth it driving that far? I would probably have to ask about what's actually in the basalt - but do mines analyse the mineral content. On the website they say it's silica free- good or bad? And if I ask whether that basalt is paramagnetic or not they probably think I'm completely mad. Anyway I'll have to wait until the fires are over the roads are closed most of the time! Is it worth the effort and how much do you use on a bed?

Couple of things, what are you hoping to gain? what mineral that you are missing are you hoping to find in the basalt dust? Also what is the underlying bedrock where you are? For example mine is chalk so I have very limited minerals available to begin with (but lots of glacial erratics so that provides pretty much everything)
They will look at you oddly if you ask about magnetism, because as far as I am aware ALL basalts show some magnetism. it is one proof we used in the theory of tectonic plates after all.

And my last point, no silica? well then it's not basalt Basalt by definition has around 50% silica. What they may mean is that the rock is undersaturated in silica (probably still pushes it out of the basalt classification but hey ho) meaning there is no free quartz in the matrix, for adding minerals to soil silica is just filler so the less of it the better.

What we have is fill over swamp and on this did start building my soil, with tons of woodchips, compost, leftover potting soil and so on. The soil test I did two years ago came out quite reasonable but my garden could grow better. I reckon that (apart from my new compost brew machine) more minerals, in general, would help. I know that there are basalt mines which are 'paramagnetic', because boral did some research in the past on that but they dropped it (they were able to do enough business with the building boom). That particular mine is a smaller company.

Angelica, if you mean by "swamp" really mucky wet soil, or actual standing water, or occasionally slowly flowing water?   The types of plants you intend to put there will always find that high level of water, no matter how much fill you put there, so they need to be plants that can deal with their roots in water.  There are only certain trees and perennials that can live under conditions of a lot of water, which is usually considered anaerobic conditions.

If it's just annuals, then that would be easier, although even tomato roots can go down 5 feet.

Is it possible to dig the swamp deeper, make a small pond, then plant on the edges?  Or drain it to the side with trenches, then plant downslope of the trenches?