sentences:  Some "Noir belge marble" deposit belongs to a fine-grained calcareous sedimentary formation dated Frasnian era (Upper Devonian – around 360 million years ago) and located on the northern border of Namur sedimentary basin.A few black limestones located in the lower Carboniferous (near the city of Dinant) 
  
  To the naked eye the differences between the black marbles from different quarries are almost impossible to determine.Good "Belgian Black" is dug as an inconspicuous grey stone but becomes immaculately deep black and shining as it is polished.