You can easily imagine the miners in the next 1000 to 5000 years drilling down through ice and water to get to the iron core on Ganymede

 However, the most valuable thing on Ganymede likely is the water itself, not the iron though that would be valuable too. Because the water can be through electrolysis easily with solar power turned into both oxygen and hydrogen.

The Oxygen for breathing, the water for drinking, eating, washing dishes and clothes and bathing and traveling throughout this solar system and others, the hydrogen for hydrogen cells or for Fusion power to power spaceships in the future. This makes the water and iron core extremely valuable for future space travel and human survival traveling this solar system and others.