* The colour in pink diamonds is mainly generated through a process called plastic deformation, which distorts the crystal lattice at the atomic level.

* The process happens when very intense heat and pressure are applied to a diamond that has already formed in the earth and can take millions of years.

* This is different to other fancy diamonds, where the colour is generally linked to the presence of trace elements, such as nitrogen and boron.

* The pink colour can also be generated in the laboratory by subjecting synthetic white diamonds to radiation and high heat or by another process called chemical vapour deposition.

* Synthetic pink diamonds are generally light in colour and don't show the depth or uniformity seen in some natural pink diamonds.

* This difference probably occurs because the natural process of plastic deformation can't yet be replicated in a laboratory.

* Natural pink diamonds also have a tendency to fluoresce blue under long-wave UV light. Some white diamonds also exhibit this reaction.

* Synthetic pinks tend to fluoresce orange-red.

* The global market for pinks took off in the early 2000s after US actor Ben Affleck proposed to singer and dancer Jennifer Lopez, presenting her with a 6.1 carat pale pink diamond balanced with two white side diamonds.

* He reportedly paid $US1.2 million for the square-shaped bling, much less than similar stones have fetched more recently.

Australian Associated Press