(IDEX Online) - A rare 5.22-carat Kashmir sapphire is expected to fetch up to $480,000 at Bonhams' New York Jewels sale later this month.The cushion-shaped mixed-cut gem was discovered high up in the Zanskar region of the Himalayas in the 1880s.It is certified as unheated and is set in a ring with 10 diamonds (approx four carats) in 18k pink and silver-topped gold. It is estimated at $280,000-$480,000.The rarity of Kashmir sapphires is legendary. Most were mined during a brief window of just seven years, until 1887, and only in the summer months because the snow. Last December a Kashmir sapphire and diamond brooch, circa 1910, exceeded a high estimate of $800,000 to sell for $1.11m at Bonhams.