none that I am aware of. they pose the same problems that stone chips do. so as you know what you are doing with them go for it. I assume you have a membrane down to stop them disappearing into the soil.

Just be carful with the mower as it can pick them up and shoot them out at high speed ...
Gg

Good point...would be like shrapnel! Better wear your shinguards! :)

Hi, I am replacing little or no membrane and meagre stones that remain, Sea. Ok Gnome and Karen, will do, but there are bricks separating them, fingers crossed. I'll go ahead and order some. Thanks very much.