Dealing with staining caused by roundup! - Roundup causing staining on cobbles

[nickie]

We recently had grey sandstone cobbles (Global Stone Paving Old Rectory monsoon black) laid as our new path. Unfortunately a sprayer filled with (diluted) Roundup dripped along a portion of the path and I now have little black spots on quite a few cobbles. As the Roundup is a clear colour I was a bit surprised it didn't just dry and disappear. Tried washing off with water but no luck. Have you any suggestions please - and one possibility to avoid future problems, can we seal the stone? Do you know if sealing produces a slightly darker shade (wouldn't mind if it did actually) and can you recommend a good sealant?

[RAPressureWashing]

Never known round-up to stain before? can you post a photo of the black marks/stains.

[nickie]

I have emailed the picture to you - I couldn't work out how to upload it here easily.
Nickie

[nickie]

Glad to say that these stains faded away after a week. The Roundup manufacturer thought one possiblity was that the oil content in Roundup that helps it stick to leaves helped it penetrate the stone - anyway maybe it just needed a long time to fade - maybe the sun helped. Anyway, if it happens to anyone else, there is light at the end of the tunnel!

[Mikey_C]

thanks for the update