ivory will show age lines, sometimes you can see it, at other times use a 10x loupe....you'll see a cross-hatching...a diamond or V shape pattern
ivory will have a creamy white, yellow, tan coloring.....under a blacklight, ivory will show up as brilliant white while bone or resin or plastic will be dull color...then theres a hot pin test..not recommended...heat a pin to red hot..touch the surface....nothing much will happen with ivory...will cause a little burr......with others, it will melt into the surface.....with ivory, you'll smell a decaying smell...like tooth decay
heres some pieces...the large piece is follisized walrus...the eagle carving, mammoth...rest are elephant....except for raccoon, resin....bear, polymar..hope that helps...oh, and if someone tries to stain.."age" the other stuff to look like ivory, a Q-tip with alcohol will remove the stain