A rare 41.50-carat diamond will headline the spring Magnificent Jewels sale at Sotheby’s in New York, the auction house said Tuesday.

The round, D-color, flawless, triple Ex, type IIa diamond is expected to garner up to $5.5 million at the April 15 sale, Sotheby’s noted.

Other highlights include items from the private collections of the late American actress Rhonda Fleming and of Miami-based philanthropist Patricia Wallace.

Dubbed “The Queen of Technicolor,” Fleming was widely known for her prominent roles in some of Hollywood’s most celebrated film-noir productions.

The actress favored emerald pieces, as they accentuated the green in her eyes. On offer will be her necklace suspending seven fluted emerald beads, accented by diamonds, with matching earrings. The items, presented as a set, have a high estimate of $20,000.

The more than 20 pieces from Wallace’s private estate feature Cartier, Van Cleef & Arpels, Bulgari, and David Webb. In tribute to Wallace’s philanthropy, three panther-inspired jewels by Cartier and one by David Webb will be sold to benefit Panthera, a wildcat-conservation organization. A Cartier colored-stone and diamond Panthère bracelet is predicted to fetch up to $80,000. Another piece from the collection, a Bulgari diamond ring weighing 22.11 carats, carries a high estimate of $600,000.

“My mother would be pleased that proceeds from her collection will help conserve the big cats whose forms are represented so beautifully in jewels and metal throughout her collection,” noted Wallace’s son, Mark Wallace.

Graff, Tiffany & Co. and Vendura are among the other brands featuring in the auction, with a cushion-cut, 28.01-carat Kashmir sapphire ring from Tiffany listed for up to $3.5 million.