Gritty Pearls

I have a 22 inch strand of pearls. I inherited them from my grandmother, who received them from my grandfather, who, I believe, purchased them in Japan. I know they are real, because they are heavy, not all exactly the same shape, have a pink tone in the light, they make a gritty noise when I run them on my teeth or together. I need to sell them, however, I need to know their value, before I try to go sell them.
Many thanks!