Quarry material for minerals in the soil - right material?

I haven't done a soil test yet, but Phil Nauta writes that rock dust can be used in any garden regardless of a soil test.
I called the local landscape supply (Australia) and what they told me that they have "black metal dust" but cannot say weather
it is used for gardens not from what quarry it comes. Is this the right thing? What sort of stone is it?
and finally, if it is the right thing how much do I spread per m2? A double handful or more??
Do I work it into the soil or just put it on the surface?
And if I plant trees do I put it in the hole or on the surface?

If it's locally quarried, then it's not going to do you much good. Jared Diamond, in one of his books, explains the problem of lack of minerals in Australian soils. It has to do with the lack of volcanoes in Australia or upwind of Australia. Unlike Eurasia, Africa and the Americas, there is very little volcanic ash falling down on Australia bringing new minerals. Volcanic dust can travel thousands of miles, but the only thing upwind of Australia for thousands of miles is lots of Pacific Ocean.

If you want to improve the mineral balance in your soil, and you are in Australia, you are going to have to bend one of the rules of Permaculture and bring in some external inputs. Like Himalayan rock dust. Or real dolomite from the Dolomites in Italy.

If you look at my post on composting alkaline batteries, you can also use that method to bring in chelated minerals. Batteries contain zinc and manganese, but you can use the same chelating method for other metals like cobalt, molybdenum, iron, vanadium, etc. You may want to check with a local soil scientist to find out what elements are in particularly short supply in your area. With that knowledge, you can keep your eye out for some industrial waste product that contains those elements and maybe even get paid to take their waste off their hands for them.

Another possible source of minerals is seaweed. Ocean currents move the minerals about and seawater typically has the same trace elements in it anywhere you sample it. It may be enriched locally around the mouths of rivers, but once you get out into the main circulation, concentration gradients go away. The only problem with seaweed is that it is a lot of water, a lot less carbohydrate, and a tiny amount of minerals. If you are close enough to the ocean that you can get truckloads of dried seaweed and can use that to mulch your garden, then that may solve your mineral problem.

I use seasol which is seaweed we rarely go to the beach.

John Elliott wrote:If it's locally quarried, then it's not going to do you much good. Jared Diamond, in one of his books, explains the problem of lack of minerals in Australian soils. It has to do with the lack of volcanoes in Australia or upwind of Australia. Unlike Eurasia, Africa and the Americas, there is very little volcanic ash falling down on Australia bringing new minerals. Volcanic dust can travel thousands of miles, but the only thing upwind of Australia for thousands of miles is lots of Pacific Ocean.

I disagree with these statements. Bedrock geology of Australia is quite variable and is full of volcanics and igneous intrusives. The volcanics are primarily located in the eastern part of the country, but the igneous intrusives are throughout the county. It is true there isn't much ash currently falling on Australia but there is more diversity of geology than many countries. While mineral poor soils may be common - there are many local sources of minerals for amendments.

Also, a local quarry can have significantly different mineralology than your particular location. Of the six quarries near me, only two have essentially the same geology as my home.

I'm not sure what the 'black metal dust' in the original post is. But I would make sure it isn't slag or something else you don't want.

It's some sort of quarry material, but with unknown mineral content.

We live in the U.S., but I went to a monument place, you know- - - tombstones. They gave me all the finely powdered dust I wanted, told me to come back anytime. Most of it is granite dust, I think, with maybe some sand in there too, IDK... The guys working there were very familiar with my request, say they have gardeners in there "...all the time." May be worth looking into for you... Another person on this site said they get wet dust from a place that cuts granite counter tops. That'd be better, really... Best, T

Thanks that is a great idea! I wouldn't ask the countertop guys though because most of what they are doing is cesarstone which is a concrete.
How do I know about the mineral content of the tombstone dust?