Blue diamond prices climbed in the third quarter due to lower supply, according to the Fancy Color Research Foundation (FCRF).

The price of fancy blue diamonds grew 4.7% year on year in the three months ending September 30. They also rose 0.4% from the second quarter, the organization said in a statement Tuesday.

The Fancy Color Diamond Index, which tracks prices of yellow, pink and blue diamonds in Hong Kong, New York and Tel Aviv, showed an overall decline of 0.2% year on year for all the fancy-color categories, with prices increasing 0.2% from the previous quarter.

“As far as supply is concerned, 2017 and the year before were record-low years for blue fancy-color diamond production from mines,” said Eden Rachminov, chairman of the FCRF’s advisory board.

“The majority of the blues that are coming into the market are pre-owned stones. Manufacturers have seen a significant drop in availability across all sizes and qualities, and consequently prices have continued to increase,” he added.

Prices of fancy yellow diamonds slipped 2.5% year on year and were 0.1% lower than in the second quarter. Prices of pinks fell 0.6% compared with last year, and edged up 0.3% from the previous quarter.