Archaeologists have uncovered a rare stone tomb estimated to be almost 4,000 years old on the Svinesund plateau near Halden, Norway, during excavations ahead of a planned industrial development. Known as a hellekiste, or “slab chest,” the structure was built using large stone slabs and contained a flint arrowhead, an amber bead and decorated pottery. Researchers are examining charcoal and burned bone found inside the grave to determine its age a…