UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 OR ¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF SECURITIES EXCHANGE ACT OF 1934 For the transition period _______________ to _______________ Commission file number 001-37362 Black Stone Minerals, L.P. (Exact Name of Registrant As Specified in Its Charter) Delaware 47-1846692 (State or Oth ...