Blackstone Inc. (NYSE:BX) is planning an initial public offering for Building Materials Europe B.V. that could value the business at as much as €6 billion ($7.1 billion), people familiar with the matter said. The private equity firm is working with Lazard Ltd. and plans to select underwriters for the potential share sale in the coming weeks, the people said, asking not to be identified because the information is private. It is considering listing the business in Amsterdam in 2022, according to the people. An IPO would mark a relatively quick exit for Blackstone.