Two paintings by the Impressionist master Claude Monet that have never been shown in public are to be sold in Paris next month by the billionaire Schlumberger family of France, auction house Sotheby's said Thursday.

"Iris", a large painting Monet completed toward the end of his life, has been valued at 22 million to 30 million euros ($25-34 million), which represents "the highest estimate ever given for a painting offered at auction in France", Sotheby's said as it unveiled the sale at its Paris headquarters. 

It has never left the Schlumberger family's home in Paris after being acquired by Jeanne Schlumberger (1889–1983), who was described as "a brilliant art collector" by Sotheby's art department co-head Thomas Bompard.

Alongside "Iris", three other canvases by Monet are included in the sale on October 22, among them "Saule Pleureur" (Weeping Willow), valued at 9-12 million euros. 

The sale comes in the year marking the centenary of Monet's death on December 5, 1926, which is being commemorated by two Paris exhibitions opening in late September: "Monet, Painting Time" and "Stories of Landscapes, from Monet to Hockney." 

The Schlumberger collection, which will be shown in Hong Kong and New York before the sale, also includes three works by Paul Cezanne, among them "La Ferme" (The Farm), "the largest work by the artist ever to be offered at auction," estimated at 600,000 to 800,000 euros.