but why a speciman of native British granite wasn't used I don't know!
Easy. To extract granite, you would find that your quarry had become an SSSI and a World Heritage Site, your buildings had become listed buildings so you couldn't use them any more, your access road had a 7.5tonne limit so the posh retired folk don't get their life disurbed by some work going on, a Conservation Area had sprung up nearby, the blasting noise had triggered a Noise Abatement Order, Health and Safety requirements mean that £2million of handling machinery is required because we can't lift more than 10kg without an exoskeleton.
You know, the usual obstacles to doing business.
Chris.
P.S. I wish I was joking.