Complex sentence: Notably, the Coin Cabinet and the mineralogical collection were extensive, private collections belonging to the archduke himself, and form the spiritual heart of the museum's departments in disciplines from both the humanities and the natural sciences.
Split into simpler sentences: Notably, the Coin Cabinet and the mineralogical collection were extensive, private collections belonging to the archduke. They form the heart of the museum's departments in disciplines from both the humanities and the natural sciences.