I know it’s way off topic,but rock known as gritstone isn’t granite,but a form of ‘sandstone on steroids’,the hardrock you see on crags often only goes so far into the rock,which is a patina created by weathering,and underneath that is usually pale brown and easy to rub away with your finger.
Quarried gritstone is a little bit different,where it’s more solid in nature all the way through,it’s still ‘sandstone on steroids’,and it isn’t called granite.
MBUK got it wrong when they called the rock granite in thier feature on somebody riding along a high wire between two 30ft boulders.
Personally i find BB7 disc brakes to be fine in use,and my pads have lasted ages,i just cycled down my drive quickly a few times and braked hard at the bottom. I did an endo by mistake after fitting my front one and pulling the lever like on V brake front brakes.