Iron Stone Real Estate Partners’ plan for 1,240 apartments across six buildings at 4601 Market St. in West Philadelphia has all the necessary approvals and is shovel-ready. The residential project is part of the second phase of Iron Stone’s redevelopment of the property between 46th and 48th streets. Iron Stone spent $70 million to redevelop the former Provident Mutual Life Insurance Co. headquarters that was built in 1927 and turn it into a medical and education hub. The residential project is among several in Philadelphia waiting out a challenging time to begin construction.