Final answer:
The sickle that Cronus used to castrate Uranus was made of adamantine, a mythical substance known for its indestructibility in Greek mythology.
Step-by-step explanation:
The sickle that Cronus used to castrate his father Uranus was made of adamantine. In Greek mythology, adamantine was a term used to describe any especially hard substance, either composed of diamond or some type of indestructible, mythical material. This event is a part of the mythological stories of the Titans and is not historical fact but rather a form of ancient literature that gives insight into the beliefs and cultures of early civilizations. The focus on such a material underscores the magical and powerful nature of the gods and their artifacts in mythology.