I seem to recollect that Grambler was connected to Sparnon? Not absolutely sure. Used to live across the field from grambler, there was a shaft just off the Redruth to St day road just off the turning that leads up to Gramblers engine house, this was back in the late seventies, all the builders (and others) used to dump all their crap down it until it was filled up, It was then covered with soil, about a year later after wet weather some ominous looking cracks appeared arround where the shaft collar was.
I found a kibble in the dumps at Grambler but gave it away years ago.
Lozz.