Well, this was a struggle for me despite being the theme early on (from 18A). Finally got there with a on of help from you all, many thanks and thanks to Imogen for an enjoyable challenge and some good memories.
A special shout-out to the poster who linked 26a to the theme. I got the stone straight away but had a connection tickling in the back of my mind until you brought it forward.
I spent a long time looking for Mr Rusty but I think he is missing - I'd almost convinced myself that his first name was Ebenezer and he sat at 4a, which I couldn't parse but messed up my NE corner for a while.
I should say 'time for bed' but, as do often, I'm finishing Saturday's puzzle in a Monday morning early waking period so I'm snugly tucked in already