Greensand used in gardening is a complicated mineral called glauconite. It seems to have a little bit of everything in it.
Interestingly, while it has significant iron in it, the iron is ferric iron and not the available ferrous iron. It seems that there are other properties of glauconite that allow other bound up iron already in your soil to be released, so that seems to be the mechanism by which it greens up the lawn. If you don't have an iron problem, greensand will not help you. Most grass is yellowish because it is not getting fed with nitrogen. Any organic fertilizer will help with that.
_________________ David Hall Moderator Dirt Doctor Lawns Forum
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