WASHINGTON (CNS) -- A special one-time national collection will be taken at U.S. parishes at Masses on Mother's Day, May 14, to support the mosaic ornamentation of the Trinity Dome, the "crowning jewel" of the Basilica of the National Shrine of the Immaculate Conception.

The mosaic will depict the Trinity, Mary and 13 saints associated with the United States or the national shrine, the four evangelists and words from the Nicene Creed.

The finished dome also will mark the completion of the national shrine, according to the original architectural plans for the church set to mark its centennial in 2020 -- the 100th anniversary of the placement of its foundational stone.

The U.S. Catholic bishops approved the special collection in November 2015 during their annual fall general assembly. The last time a national collection was done for the shrine was in 1953.

Last October during the blessing of the workspace where the new mosaic will be installed, Washington Cardinal Donald W. Wuerl said the work of art "will be a wonder to behold." It is expected to be completed at the end of 2017.

The mosaic work is being done at the Travisanutto Giovanni mosaic company in Spilimbergo, Italy, and is being shipped to the national shrine in 30,000 sections weighing 24 tons and composed of more than 14 million pieces of glass.

Builders, church leaders, choir members and journalists gathered atop eight floors of scaffolding -- 159 feet high -- in the national shrine for the blessing.

Cardinal Wuerl, who is chairman of the shrine's board of trustees, offered prayers during the blessing for the success of the project and the safety of the workers involved. He said the shrine puts into "image form" the message of the Gospel and does so "in a way that everyone can bask in its beauty."

He said the finished dome, with its particular emphasis on American saints, will remind people of the "face of who we are and the face of God." He also said it will reflect "living images of God and living images of everything we are capable of being."

In introductory remarks, Msgr. Walter Rossi, rector of the national shrine, stressed the parallels between the mosaic design on the dome and the very character of the shrine itself -- often described as America's Catholic church -- representing a mosaic of Catholic parishioners from every corner of the globe.

Both Cardinal Wuerl and Msgr. Rossi noted that the scaffolding itself, allowing the workers to complete the work on the dome, was an engineering feat. Work on the scaffolding began early in 2016.