Robert Smithson, Detail of Mirror and Crushed Shells showing map of Sanibel Island, Florida
On July 9, 1969 Robert Smithson wrote the following letter to Andy Warhol about Mirror and Crushed Shells:
"Dear Andy, This is to certify that the Mirror with Crushed Shells (Sanibel Island) is an original work of art. It consists of three mirrors which may be restored if broken, and one burlap bag of crushed shells collected by the artist at Sanibel Island, April, 1969. If any shells are ever lost, the owner has the right to restore the work by collecting more shells from Sanibel Island (northern part of island – see map of site which is part of the work). The three mirrors are held in place in a corner by the pressure of the shells only. (See photo). The work is owned by Andy Warhol, and can not be duplicated.