• Location: Sahara Desert, Morocco
• Formula: SiO2
• Mohs Hardness Scale: 6-7

Most rocks that we’ve sent you so far were created over hundreds, thousands, or even millions of years. But this one formed lightning-fast, literally. This is a fulgurite, which some people call fossilized lightning. These silica-based formations happen when lightning strikes the exact right surface, and the heat generated from the strike melts the silica, which then cools into a hollow tube.

Because no two lightning strikes are the same, every fulgurite is unique, and the way they look can tell us about what kind of lightning made them. And geologists can tell how often an area was struck by lightning based on how many fulgurites they find there, which gives insights into what the climate was like in that area, and even helps them model long-term climate shifts. All thanks to a mineral that forms in the blink of an eye.