Haven't seen thread for this so here you are, apologies if duplicate obvisouly.
Scared explorer came back with 60 granite after a 9 day prolonged, usually this is in the few hundreds as he has base x4
Sturdy shovel appears to have zero effect, equivalent explorers with/without skills returning the same from equivalent searches.
So, I have nearly 100 explorers, all now booked with 3 sturdy shovel, doing typically 3-4 mediums and one very long/prolonged over a day.
I'm owed 9% of that thanks.
Lots of reports on chat of geos having similar issues.