Is what was narrated on the authority of Ikrimah from Ibn Abbas—that three things descended with Adam: the Black Stone, the Staff of Moses, and iron—authentic, definitively proven, and agreed upon by consensus?

The chain of transmission for what was narrated from Ibn Abbas is not authenticated. However, the Hadith of Tirmidhi and Al-Albani is authentic, stating that the Black Stone descended from Paradise whiter than milk, and the sins of the Children of Adam turned it black.