Those planets that didn't serve as a barbecue on a skewer, became chandeliers whose orbits and atmosphere transforms into metals, diamonds, and other precious stones, die petrified, from the outside as well as the inside like precious stones.
3. 55 Cancri E
This planet is twice as big as Earth, but it weighs eight times as much! As it happened in that great part of its mass being composed of carbon, it is very explored the respiration doesn't work, there in those regions, they were completely taken by carbon, multiplying without stopping, in which their surface is full of diamonds.
4. Hat-P-7b
With high aluminum oxide precipitation on its dark side, this planet can experience storms of sapphires and rubies.
Each of your planets once, ages ago, they were inhabited, involved in the wars of the galaxies, their inhabitants were corrupted and contaminated by diamonds, and when breathing the air it dissipates and accumulates diamonds.