Stonehenge made by Legion Paper in the USA is an Acid free/neutral pH, 100% Cotton paper.
Originally created in 1972 as a print-making paper, it subsequently became popular for artists using many different mediums.
An excellent silkscreen paper with its ability to take as many as 50-75 colours, printed one at a time, maintaining perfect colour registration thanks to its incredible dimensional stability.
Favoured by the Colored Pencil Society of America, it has the ability to take multiple layers of wax or oil based coloured pencils without any buildup, allowing colours to penetrate and absorb into the surface of the sheet.