Scientists from the Lawrence Livermore National Laboratory, the University of Rochester and the University of California-Berkeley noted that most natural diamonds result from the compression of carbon-containing minerals under high-temperature conditions at depths of 87 to 120 miles over periods ranging from 1 billion to 3.3 billion years.

The scientists said they applied laser-generated shock waves to rapidly compress a diamond and found natural diamond crystals under shock-wave compression withstood nearly one million atmospheres of pressure, but collapsed and melted in one-billionth of a second under pressures between 1 million and 10 million atmospheres.

The authors said their experiments simulated conditions found on icy gas giant planets, such as Uranus and Neptune, where icebergs of diamond could float on seas of liquid carbon.

The study that included then graduate student Stewart McWilliams, the study's lead author, and Lawrence Livermore's Jon Eggert, appears in the journal Physical Review B.

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