Its called Schreger lines.. they are not rings though.... more commonly called "cross hatchings"... for the lines cross over each other in a criss cross pattern.
JFYI... you can easily tell between bone and ivory using hot pin test...Bone smells like burning hair when hot pin is used.
I did say SLIGHTLY more difficult, as both produce a nasty smell that the average person who has not tested both may not be able to tell the difference with just the pin test. Other things they can look for is in bone the remnants of the structures that delivered blood that are often decribed as flakes or small channels, vrs the ivory which has faint long tubular structure. So yeah not as simple as testing between the plastic fakes, and not as complicated as determining which animal it came from if heavily carved.
