In reply to Dave Hewitt:
The leaving of the urn at the site where the ashes are 'scattered' is often advocated as a solution when someone posts a query on the internet of the sort: "What do I do with an empty cremation urn'? I've even seen the suggestion that, for ashes tipped into the sea, you might choose to heave the urn into the ocean as well.
I'm not sure if funeral directors give any advice on the environmental aspect of disposal once the cremation is over.
I still have a brown plastic box that contained my brother's ashes which were scattered in a local river several decades ago. I've never really been sure what I should do with the box- there is a small residue of dusty ash on it, and it seems disrespectful to put it in the recycling, bin it, bury it somewhere random, or burn it. With hindsight, I should have washed it out in the river, then sent the box for recycling.
I suppose whatever the material of the 'urn'- cardboard, plastic, wood, or metal, it's going to be visually intrusive, if left in a mountain environment.
I wonder if the sort of people who leave urns in such places are themselves hillgoers, or are they just grieving relatives with the desire to put a mountain loving person's ashes somewhere they thought might be appropriate?