"Julia," an elaborate fractal-inspired necklace set with 423 diamonds and 1,739 sapphires, is expected to sell for 25 million zlotys or more at DESA Unicum's private sale in Poland.

(The zloty is the official currency of Poland. Twenty-five million zlotys is equivalent to about $6.2 million.)

Designed in 2009 by Aussie Marc Newson for the French luxury brand Boucheron, the 18-karat white gold necklace includes more than 125 carats of gemstones and required more than 1,500 hours to complete. The 2.5 carat, E-color, VVS2 diamond at the center of the piece appears to be floating.

Billed as the most expensive piece of jewelry ever offered at auction in Poland, the design's fractal spirals feature a diamond-intensive center that transitions to light blue sapphires and then to dark blue sapphires as the gems radiate outward from the center.

A fractal is a complex geometric pattern that when viewed at any scale repeats elements of the overall pattern. Fractals can be seen in sea shells, fern leaves, sunspots, spiral galaxies and the structure of human lungs.

According to the Warsaw-based auction house, "Julia" is one of the most expensive jewelry pieces ever sold by Boucheron. It even caught the eye of Karl Lagerfeld, who featured it at one of his haute couture shows in Paris.

"Julia" honors French mathematician Gaston Julia, whose work described how fractals are formed.

The necklace had been on public exhibition from October 22 to 26 in a guarded case at the auction house's gallery. The sale of "Julia" will take place under a private sale tender. After the necklace has been inspected by people interested in purchasing it, confidential tenders will be accepted. The last day to make an offer is November 5.

Credits: Images courtesy of DESA Unicum.