What is the pH of limestone dust?

steve22802(7a VA)April 29, 2007

Hi all,

I have a walking path that is topped with something I get from the local quarry called Quarter Inch dust. It has small limestone (1/4 inch) gravel mixed with very fine limestone dust. I've noticed that some plants (usually the ones that like well drained soil) creep out into the path and really seem to like growing in the 1/4 inch dust path. So this got me curious as to what the pH of limestone dust is. This is not a white powder like lime you get in a bag. The rock and dust are gray.



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The pH of crushed limestone that I have seen is around 8.0 something so your stone would be somewhere around the same.

    Bookmark   April 30, 2007 at 7:04AM
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pablo_nh(z4/5 NH)

Limestone is calcium carbonate- from which we get lime. Lime dust is... lime. Not quick, slaked, or hydraulic lime- just lime.

Do you have a normally acidic soil?

    Bookmark   April 30, 2007 at 7:45AM
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steve22802(7a VA)

No my soil is alkaline clay (pH 7.6 according to a soil test I had done when seeding a new lawn) you can see gray limestone protruding from the ground all around my county (Rockingham county, Virginia.)

- Steve

    Bookmark   April 30, 2007 at 9:17AM
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As a geologist I'd have to know the asociate materials of the original limestone. A lot depends on the matrix (think of marble vs crumbly mortar). Probably a rating of anywhere of the high 7s to 8.6.

Remember, however, the 'dust' is not all soluble (marble vs mortar). Also, your rainwater is probably around 5.5 or even 5.3 and probably offsets any leaching out from the dust. The 'stuff' in the cracks, although sort of limey, might actually not be any more base or acidic than the surrounding soil.

You can sometimes speculate as to the ph of the soil by what weeds easily grow.

    Bookmark   April 30, 2007 at 5:48PM
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