This is the beautiful Pomponio Sheer Indigo Fabric by Ralph Lauren, a fantastic sheer and summery fabric. Unfortunately my pictures do not do it justice. It comes in the Indigo colorway.
Its official description is: "A 100% linen wide width sheer now available in 7 colourways. A perfect co-ordinate to any of the new and existing prints, as well as working wonderfully alone for understated luxury."
Measures: 110cmW x 90cmL
The Pomponio reference belongs to the "Signature Half Moon Bay" collection: "Exuding a casual yet modern sensibility, an eclectic mix of stripes, paisleys, and embroideries and light-as-air sheer fabrics are enlivened with a faded palette of washed blues, sunbaked reds, antique whites, and creamy neutrals to capture the bohemian spirit and ease of the Northern California coast."