-Grinding, I'm not sure but I'd lean towards no if I had to guess as they have a whole lotta stone to pick from, it naturally has flat spots, irregular shapes, angles etc. *I didn't buy a pre-assembled piece from them.Looking at the stone closely, do you think they grind the faces before they glue them? How thick are some of the glue joints, I'm guessing the glue is a similar colour to the rock?
-Joint thickness, I think the only way to look at glue joints is by examining their photos but some look quite close and others not so flat-flat and tight.
-Glue, I know they use a superglue of some description which is clear although they describe it as cyanoacrylate glue which is just a quick drying superglue.
'Ancient stone' they told me was a stone which they had exclusive access to from somewhere in Poland but I cannot remember where if they did tell me, someone with Geological knowledge might be able to assist further here and help you find a stone with similar properties.
From experience I know choosing a stone with quite an even colour will help you transition between stones without sticking out so much which is something maybe worth baring in mind too.
The type of stone Aquaman uses I don't think lends itself to shaping anything like the Cotswold stone you mentioned earlier but the Cotswold stone would need to be sealed in my opinion, maybe other people have thoughts on using softer stones which could be shaped and sealing them afterwards? - Opens up a whole new world and a very different method.
I'd also guess if you're buying that much that a cheaper way of doing it could be buying direct from a distributor and just getting a bulk bag plonked on your driveway, something worth looking into maybe?
I'm going for more of a stone jungle using a whole range of plants to get a range of colours and textures
As ever I'm intrigued.I'm still working out a plan.