Ive discussed this topic with several of you, and it has been the general concensus that we need a thread on this subject. It is an amazing subject, one that I have been and still am studying. I do not claim to be any kind of an expert on this subject, (at all), but I've been working on this with a friend who does know quite a bit about it and so have learned at least some basics. Rock dust! Simple, powdered, shattered, ground, screened rock! First, let me quote from something that Lumper and I were discussing regarding soil - "Soil: rotted plant and/or animal materials with shattered rock. Here again we can see how basic plants are to the development of this planet. It is algae (the most basic plant) that over the eons pulled thin shattered layers away from the rocks leading to the development of what would become 'soil' - that is soil at its basic definition. Sticks, rocks, etc. would be considered 'amendments' by gardeners or something close. Minerals: while Â this is completely inaccurate from the perspective of a geologist or even a botanist, I'll use the layman's definition of a mineral as an Element that can be derived Â from a mined material, Â i.e. shattered rockÂ So, now that we have a basic definition of "soil" out of the way, to those that do not have rock dust in thier soil mix, by rights, this soil is incomplete. We need the rock dust in our soil mix to make it complete. I'm talking about actual rock dust here; ie: granite meal, glacial rock dust, basalt dust, et al. I'm not talki g about rock phosphate or clays (this is for a different post) - I'm just talking about simple, ground rock dust. The real question here is WHY are these dusts so important? Again, I'm going to quote LD here: Contrary to the misinformation passed around garden forums (of all stripes), there are not 12 'things' that plants need. That was the theory behind Liebig's Law of the Minimum. Liebig was the chemist (not botanist) who dropped the NPK bomb on the world in the 1840's in Germany. The book 'Bread From Stones' was written shortly thereafter that refuted Liebig's theory (which were based on Carl Sprengel's work). Â "Bread From Stones" is available online for free - a must have for a guy like you, i.e. serious organic gardener.Â The fact of the matter is that there aren't 12 Elements needed but rather 83. Keep that number in mind as you look at plant materials that you might consider using. All plants accumulate these 83 Elements and some plants that do a better job are called 'healthy' by nutritionists and we refer to them as 'bio-nutrient accumulators' and in the dietary world Kale is a better accumulator than Iceberg lettuce so we use terms like 'more nutritious' or 'healthier' - that's from the Elements that are accumulated - Phosphorus, Calcium, Potassium, etc. In the sustainable/organic gardening and agricultural paradigm, we call Comfrey, Kelp, Alfalfa, et al. nutrient accumulators. Same Elements but different terms for the same thing. In a soil shattered rock (rock dust) provide a number of things: 'anchors' for many fungi strains. While it is true that endo & ecto mycorrhizal strains 'bore into the roots' like a corkscrew that is not the case with the majority of fungi in a soil. Even in the brewing of an AACT people who know what they're doing (like Microbeman) add small amounts of some kind of rock dust not to enhance the 'mineral level' in the brew but to provide an anchor for the fungi to attach to and then extend their length. Another benefit that rock dusts provide is structure in the soil which equates to aeration paths. Paths for not only air but water to move freely in the rhizosphere.Â So, now we know that rock dusts provide several benefits, first, "mineralization", and also pathways for air and water, and most importantly, anchors for bacteria/soil life to latch onto in our soil. After much reading and discussions with LD, the REAL BENEFIT comes from ENZYMES. Once the bacteria has latched onto and anchored to the rock dust, they produce enzymes. While there are many different types of enzymes, (different types of enzymes are created dependent on thier "host") one of the most important things that happens due to these enzymes in our soil is Nutrient Cycling. Bacteria do not "eat" organic matter - they utilize these enzymes to break down the organic matter for them. They excrete enzymes thru thier bodies. By having the rock dust in our soil, we have created many places for bacteria to latch onto, more enzymes are created, by more enzymes being created, more nutrient cycling happens, by more nutrient cycling happening, more organic matter is broken down into usable plant food! Pretty slick, isn't it! Again, by LD - this dude has taught me a lot, and it's cool to be able to pass this on - But here is where the greatest benefit lies (IMHO) and that is the enzymes created by bacteria (primarily) that surround these pieces of rock. It will take many, many years for this material to breakdown. Years. But the microbial activity creates enzymes and enzymes are a key component in the nutrient cycling by plant roots from other microbial activity.Â Chitin is a perfect example of what I'm trying to explain. Chitin in and of itself does not kill a single insect. It's the enzyme that is created by bacteria called Chinease and it's this enzyme that softens insect eggs preventing them from hatching. Chitin is also a key component in fungi as it forms much of the outer layer. But again, it's the enzyme from bacterial activity that is the real goal here. But let's get back to 'mineralization' again. Last winter, Acres USA Magazine had an article that featured 6 leading experts on soil from leading universities and research centers. Each individual wrote a piece which was part of this anthology. Down to each and every scientist it was agreed that complete mineralization could be easily accomplished by using kelp meal. The problem is that the recommend amount of kelp per acre is 200 lbs. That's a lot of money - imagine amending 200 acres which is a pretty small farm. But in the world of organic farmers, Alfalfa is often referred to as 'field kelp' because like kelp, Alfalfa accumulates all of the 83 Elements needed for planting health and costs 25% of what kelp costs. Comfrey, Stinging Nettle, et al. will provide a farmer or gardner each and every Element (even NPK!!! Yay! Â LOL) So rock dusts, particularly in an artificial soil like we make up even as good as it is) will do very, very little as far as 'feeding' a plant. Very little. But the benefit comes indirectly, i.e. by having these anchors in the soil the fungi increase in size (length) meaning that they can reach more hidden 'sequestered nutrients' from bacteria exudes, etc. so in that sense the rock dusts do increase plant growth, health, etc. Think about it logically - if soil rock pieces could degrade in a 3 or 4 month trip through our indoor gardens the imagine what would have happened out in the real world - the human race and all plants and animals would have died out in the first million years of their origin.Â I'm going to end this first post by putting some links to read here. This is a fascinating subject that deserves discussion here in the Organics forum. A Rock Dust Primer http://www.paramountgrowth.com/images/rockdust_sdiver01.pdf Earth Remineralization Rock DustÂ & Seaweed jerry.