Fiber recommendations for…rock hounding bag? LOL

Hi y’all! So I really love rocks and when I have extra time or when I’m traveling I’ll usually go out and look for pretty rocks. My pockets get heavy & my husband is tired of finding random rocks in his truck, so I was thinking about making my own rock collecting bag (no patterns in mind, so if you have any pattern recommendations for a good rock bag that’d be cool too).

I want to make sure the yarn that I use has the best type of fiber content so it doesn’t get gross or rip easily. Obviously the type of bag I make will be equally as important, but what fiber do y’all think I should look for when choosing a yarn? Or if you’ve made anything similar, which yarn did y’all choose!?

THANK YOU THANK YOU! ❤️❤️