Do you have a diamond ring on your finger? If so, take a second to look at it. A diamond is, without a doubt, your most ancient possession.

Scientists have shown that gem-grade diamonds were created between 1 and 3.5 billion years ago. The diamond on your finger could be nearly as old as Earth itself.

Diamonds form deep within the planet, 100 miles down or more, underneath the continents. There, the pressure, temperature, and chemistry of the upper mantle create the perfect environment for diamonds, at 2000°F.

So how did they get to the surface? Through ancient eruptions. Jets of mantle were propelled by expanding gas, some from 400 miles within the earth—far deeper than modern-day volcanic eruptions.

The eruptions blasted through these diamond zones and carried small quantities of diamonds up with them, in shafts we now call kimberlite pipes. But less than 1% of the 6,000 pipes we’ve discovered have produced diamonds economically.

All we see of the pipes today are their carrot-shaped roots, which is where we dig our most productive diamond mines. A smaller number of diamonds erode out of the pipes and end up in streams, beaches, and undersea deposits. Offshore of Namibia, giant ships vacuum them from the seafloor.

The ancient origins of this gemstone give a whole new meaning to the phrase, “a diamond is forever.” Perhaps it’s no coincidence that diamonds have come to represent everlasting love.