When I was building my house, I was running out of money, so I only built a stone wall along the public road. I used the black rocks. When I wanted to continue the wall a couple of years later, I found that the quarrying of the black rock is now illegal, you can only get the whitish-grey rocks now. trouble with that rock is that it has iron ore in it and when it rains, you get rust streaks.
Sorry, not a good picture as I was photographing the palms, not the wall.