On Saturday, June 17, just one day before the dedication of the new Helena Montana Temple, The First Presidency announced that cornerstone ceremonies have been discontinued as a part of temple dedications.
The brief statement issued by the First Presidency reads:
“Construction techniques have advanced to the point that cornerstones are no longer included in large buildings. Therefore, temple cornerstone ceremonies will no longer be part of temple dedications.”
You can read the statement published on ChurchofJesusChrist.org.