Slate chippings (Ormskirk)

Plum coloured loose slate chippings. If you have any spare, I could certainly make use of them. Over the years the slate chippings I've had have got bare in patches. I don't know what's happened to them as there is a membrane below them. I don't think the birds are eating them or worms are taking them down. It could be someone is coming into the garden and taking a pocketful over night, but it seems unlikely.