Why is it called cakravartin??

all-powerful monarch "whose chariot wheels turn freely" or "whose travels are unobstructed."

Explanation:

Derived from the Sanskrit cakra, "wheel," and vartin, "one who turns," the term cakravartin (Pali, cakkavatti ) in classical Hindu texts signifies that all-powerful monarch "whose chariot wheels turn freely" or "whose travels are unobstructed." Such a ruler's unsurpassed and virtuous rule is described as sarvabhauma

Silver is the answer i thinkhope it helds