LOCATION: Sukabumi, Indonesia

FORMULA: SiO2

MOHS: 6-7

When it comes to minerals, we usually think of them as solid and hard as, well, rocks. But sometimes, they grow in weird ways that leave little pockets inside. And sometimes, those pockets contain ancient mineral water, trapped for millennia in a crystal enclosure. They’re called enhydro minerals, and the water inside is definitely not something you want to drink. 

All kinds of weird stuff hides in those water bubbles, from crude oil to microbes. Researchers drilled into enhydro agates from Brazil and found living bacteria inside. Agates are porous, so it’s possible that those bacteria moved into their watery homes well after the agates formed, but still. If you prefer your water bacteria-free, it’s best to leave the stuff in these enhydro agates safely enclosed.