How can you tell if a rough diamond is real?

My bf found a diamond like stone when he was a child and always wondered if it was a rough diamond. We seen pictures online and some pics do look similar to it. How can we find out for sure?|||That鈥檚 a hard one..I鈥檇 say take it to a jeweler specializing in rough diamonds or send it to a gemologist lab鈥?that鈥檚 your best bet I think