Gosh I am not sure how I know, that is a good question. That is what my mother had told me a long time ago. It is really soft and does not feel like other materials I am familiar with I guess. If you know of a way for me to test it I would be glad to try.
there is a pin test where you get needle tip hot touch it on the necklace in a place its not noticed when y touch it if smells like hair its most likely ivory . I looked it up