- Chemical Formula: Fe3Al2Si3O12
- Mohs Hardness Scale: 7
People think of garnets as just one thing, but they’re actually more like a handful of minerals all stuffed into a trenchcoat. They’re usually red, but can be lots of other colors, too. That’s because they can have tons of different metal ions in their chemical formula, but still look and act like a garnet.
And while they look lovely as jewelry, they’re prized for more than just their looks. Garnets can be used to study how areas of our planet formed millions of years ago. They’ll only crystallize at a certain temperature and pressure, so when geologists find garnets in layers of rock, they know just how hot it got there.