Two massive Tennessee marble urns flank the large staircase of the Frick mansion's front façade on Fifth Avenue. The urns were part of the original design by Carrère & Hastings for the "furnishing and setting of the limestone and marble work of the grounds"; this included the front terrace, the balustrades, and six marble seats. As with the rest of the house, there were very specific instructions on the materials to be used in creating these urns, including an additional cost for plaster models. In 1913 specifications by the architects for the stone contractors, William Bradley & Son, stated: "The vases and the seats marked ‘Marble’ on the drawings shall be of the Pink Tennessee marble . . .and very fine rubbed finish. Marble shall be from the top layers of the quarries of the Victoria Marble Company, or the New Light Pink Quarry of the Grey Nagle Company, or the Light Pink Quarry of the Ross & Republic Marble Company." It should be noted that Tennessee marble is not a marble at all, but rather a pink limestone. Many of the fossils within the limestone are still observable.
The urns are one of the most prominent features of the Fifth Avenue garden, but had sustained damage over time owing to exposure to the environment. The Tennessee marble had weathered, and black crusts had formed in protected areas. These crusts were caused by the dissolution from acidic conditions of calcite in the stone, which reacts with sulfur dioxide to form a layer of gypsum made black from the accumulation of dirt and pollution within the crystalline matrix. In addition, there was a major structural problem with the urn located on the south side. A large crack had developed from the pressure caused by the freezing of collected water during winter months. The north urn had already been treated for the same problem many years ago.
In 2008 it was decided that the cracks needed to be addressed, and the Conservation Department worked with contractors — Barbara Mangum, from Sculpture and Decorative Arts Conservation Services LLC, and Ivan Myjer and Miroslav Maler of Building and Monument Conservation — to treat the urns. During this project, they worked closely with The New York City Landmarks Preservation Commission to ensure that all repairs and necessary alterations were approved. Minor stabilization measures were performed to prevent the loss of any vulnerable surfaces, before carrying out more extensive repairs. On closer examination, it was found that the south urn was almost broken in half by the crack that ran vertically down both sides. The break was joined with adhesive, followed by the insertion on the interior of additional metal cramps (large staples) across the break. The black crusts were then removed with a proprietary gel, and the stone was cleaned overall with water and soft brushes. Small losses and cracks were filled with mortar toned to match the stone. New limestone bases were made and replaced the old failing supports, and the drainage was improved within the urns to avoid future problems with freeze-thaw cycles. In addition, new, larger fiberglass covers were fabricated to replace the old copper-clad wood covers, which were too small and deteriorated to prevent water from entering the urns.