- Chemical Formula: Ca2(Al,Fe3+(Al2O)(SiO4)(Si2O7)(OH))
- Mohs Hardness Scale: 6
Epidote is a super common crystal that can be found in tiny amounts just about everywhere. Depending on the mineral inclusions, it can be anything from black and dark brown to yellow to a lovely pistachio-green. And that green hue is exactly why this crystal can help us find the origins of life on Earth.
Confused? Here’s the breakdown. Epidote forms in a few ways, and one of those is when it gets exposed to really hot liquids at high pressure. That just so happens to be a near-perfect description of a deep-sea hydrothermal vent, which is where some researchers think life could have begun. So when they spot those veins of epidote, they know there was once a hydrothermal vent there, and to start looking for microbe fossils. Not bad for a little green crystal!