Sub-fossil resin or copal is usually only thousands of years old. Copal melts and liquifies when close to a flame, while amber will soften and blacken on the surface, but will not melt. Amber also crazes, but not to the same extent. This technique can be used on smaller pieces of both resin products to tell if you have been duped into buying yellow plastic. Amber and copal run a range of colors from light yellows to orange and deep reds.
Texture is much the same and both can have all sorts of inclusions.
Copal contains high amounts of volatile terpenes from the original resin and when exposed to air gives the crazed appearance. Amber, being older, contains much less. A wound or scar on a tree will bleed resin which hardens rapidly to seal off the wound, much like scar tissue that forms on our skin. Our blood has antibodies that fight off germs that invade an open wound and so do these trees in a sense. Kauri gums don't look like conifers we see in the Americas.