Most diamonds are billions of years old, making them older than dinosaurs and even the earliest life on Earth.

Most natural diamonds were formed during the Archean Eon, a period spanning from 4 billion to 2.5 billion years ago. Geologists at the Smithsonian Institution and the Gemological Institute of America (GIA) use carbon dating and inclusions of minerals like garnet and sulfide to determine these ages. These gemstones crystallized at depths of 90 to 150 miles below the Earth's surface in the lithospheric mantle.The conditions required for diamond formation include temperatures of at least 2,000 degrees Fahrenheit and pressures exceeding 725,000 pounds per square inch. This environment allows carbon atoms to bond in a unique cubic crystal structure that gives diamonds their legendary hardness. For comparison, the first dinosaurs did not appear until the Triassic Period, roughly 230 million years ago, meaning most diamonds had already existed for billions of years before the first dinosaur walked the Earth.The journey to the surface occurred through rare, deep-source volcanic eruptions known as kimberlite or lamproite pipes. These eruptions traveled at speeds of up to 30 miles per hour, acting as high-speed elevators that brought the diamonds to the surface before they could dissolve into graphite. The youngest diamonds ever discovered are still approximately 100 million years old, while the oldest known specimens from the Jack Hills in Australia date back 4.25 billion years.