Diamonds are...

 ...as cheap as dirt.

This could become reality because somebody turned cheap plastic into diamonds.

They were very small diamonds, but they were nonetheless diamonds.

In addition to helping us understand how diamonds form on gas giants, this opens the door to turning, say, your discarded plastic water bottle into actual...actual...diamonds. It's done using lasers, and it makes diamonds that are normally made by, well, blowing things up. Or rather by highly contained explosions. On Earth, nanodiamonds are only formed by things like meteor strikes.

The nanodiamonds could be used:

* As antimicrobial agents.

* In vaccines and drug delivery systems, especially for cancer treatment.

* In tests for viral infections...this is already being done with HIV.

* In skin care.

* For after treatment of root canals and other really invasive dental stuff.

* To measure changes in weak magnetic fields.

* Other high performance sensor applications

* In optical computing

* In room-temperature quantum computing.

* In imaging systems.

If we really can make them out of plastic waste then we just discovered something really important.

It's the Diamond Age, folks. Maybe. Assuming it pans out outside the lab.