Using Granite Dust As A Soil Amendment

Q: You have mentioned using granite dust as a soil amendment. I use a talc-like material that’s a waste product produced from sand-blasting names on granite grave markers. I mix it with coffee grounds and composted leaves. I don’t apply anything else to my garden. 

A: What you have is truly granite dust, mixed with a little aluminum oxide. I can see how this byproduct of sandblasting slabs would be very fine inconsistency. The “granite dust” I was referring to is sometimes called rock dust or stone dust. It is a byproduct of crushing granite into gravel. As you can imagine, in this process there are a lot of small pieces which are screened from the larger ones. Even though it is called “granite dust” the consistency is very gritty. As far as using either material for fertilizer, both contain slow-dissolving potassium and a few other minor nutrients. Chemically speaking, it might take fifty years for your dust to decompose and release its potassium and it might take a century to release the potassium from my larger particles. Having said all the above, my first boss, Charlie Tucker, taught me an elemental truth: “You can’t argue with success.” If you are pleased with your garden harvest, you can use your granite dust with my blessings.

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