X0306 4 2019-06-10 0 0001621434 Black Stone Minerals, L.P. BSM 0001638259 DeWalch D Mark 1001 FANNIN STREET, SUITE 2020 HOUSTON TX 77002 1 0 0 0 Common units representing limited partner interests 2019-06-10 4 P 0 5350 16.44 A 40809 I By Donald Mark DeWalch Trust Common units representing limited partner interests 174272 D Common units representing limited partner interests 6749 I By wife Common units representing limited partner interests 10317 I By daughter The price reported in Column 4 is a weighted average price. These common units were purchased in multiple transactions at prices ranging from $16.42 to $16.45, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of common units purchased at each separate price within the ranges set forth in this footnote. /s/ Steve Putman, attorney-in-fact for D. Mark DeWalch 2019-06-12