Tracked by Knight Frank as one of 10 luxury investment assets along with jewelry in general, art, wine, watches, and cars,  the value of colored diamonds has appreciated 70% in the last decade, or about 12% every year, according to The 2018 Knight Frank Luxury Investment Index.

During the third quarter last year, the last period for which data is available, overall fancy color diamond prices grew 0.4% from the year before, according to the Fancy Color Research Foundation, an Israel-based diamond market information provider. Fancy vivid blue diamonds continued to outperform other kinds, rising 8.5% during the same period of time.

While all fancy pink diamonds gained only 0.5% in value in the third quarter of 2018, their valuations will likely grow faster in the coming years due to an expected shortage of supply, according to Okoyemov.

The Argyle Diamond Mine in Australia, a source of over 90% of pink diamonds in the world, is set to close by 2020.

Rare fancy pink diamonds have also set records at auction in recent years.

Last November, a 18.96-carat rectangular fancy vivid pink diamond, The Pink Legacy, fetched US$50.4 million at Christie’s Geneva, setting a  record price per carat for a pink diamond sold at auction, at US$2.6 million.

In 2017, The Pink Star, a 59.60-carat fancy vivid pink diamond fetched US$71.2 million at a Sotheby’s auction in Hong Kong. It retained the title of most expensive pink diamond in the world.

Also in 2017, Christie’s Hong Kong sold The Pink Promise, an oval-shaped, 14.93-carat fancy vivid pink diamond, for US$32.5 million, or US$2.2 million per carat.

Yellow diamonds saw their overall value rise 1.6% in the third quarter of 2018, according to the Fancy Color Research Foundation.

Only one in every 10,000 gem-quality diamonds has natural color. Depending on the intensity of the colors, colored diamonds can be even more valuable than white (or colorless) diamonds, which are considered to be of the highest quality.