Problem: I want to re-do my landscaping, but want to re-use the existing rock. The old rock has gotten brown and yellow stains on the bottom - can I clean it?
TL;DR: No, you can't.
As far as I can tell, the rock is called "Crystal White". Mine looks to be about 1" / 25mm size.
Over time, it develops brown and/or yellow "staining" on the bottom. This is likely due to oxidation.
This means taking up and re-laying down the same rock doesn't work, since half the rock will be discolored instead of nice and white. As this rock is hard to find and potentially expensive, I wanted to re-use the same rock instead of throwing it away.
It may seem obvious that you can - or can't. Some people report success in "cleaning" their rock.
I tried the following materials to eliminate the discolorations:
- Barkeepers Friend (oxalic acid)
- Stainless Steel cleaner
- TSP (premixed / ready-to-use)
- CLR (straight)
- Palmolive dish detergent
- Glass cleaner (ammonia)
- Muriatic acid
- 70% alcohol
- 20% chlorine bleach
- 50% chlorine bleach
- Toilet cleaner (hydrochloric acid)
All were soaked for at least 24 hours.
None of these had any cleaning effect. CLR made the rock stink and turned the veins yellow, and muriatic acid dissolved the rock:
None of the other cleaners had any meaningful effect.
So, if you have this type of rock, don't bother trying to clean it for re-use.