No strange rocks

Hey Guys. I don’t know if this has been a problem for awhile or if i’m doing something wrong, but I am unable to get strange rocks. I skill all the time and I have only gotten the woodcutting Rocks. And that was 2 years ago. I haven’t really noticed until i need those 10 kudos for the varrock hard tasks. If anyone has any idea why this is please inform me!
Thank you!.