A waterfall island asks the stone to turn the corner. Done well, the seam disappears and the veining keeps reading. Done quickly, every angle gives the trick away.
We mitre at 45 degrees, glue with colour-matched epoxy, and dress the joint by hand. The reveal is a single hairline.
Quartzite, dense exotics, and soapstone are the safest performers under daily use. Marble can do this beautifully too, with the same caveats that apply to any marble counter.