the materials used for ranked have nothing to dow ith how strong/dense they are (I.E. Bronze/Silver)
i wonder how long it will take for people to realize, the materials they use for ranked, are based on how shiny the material is and how common the metal is, not how strong it is.... Iron is one of the dullest metals as far as shininess or gleam goes. it's also one of the most common metals you can find. Bronze is fairly shiny, but dull. and is made mostly of copper, which is more rare than iron, but still common enough. Silver is Shinier than bronze. and has an average rarity. Gold shinier than silver. and is a very rare metal, but still common enough we aren't gonna run out any time soon. (Bronze, Silver, and Gold are the 3 olympic medals and are in this order for these very reasons) Platinum literally sparkles. and is very rare, more so than gold. Diamonds shine and refract light in beautiful ways. and are one of the most precious materials on the planet after diamond you go into master, which isn't a mineral, but you could argue "Masters shine brighter than any material" (see the metaphor?) and perhaps it's rarer to become a master at an art, than it is to find those minerals? Grandmasters shine brighter than a regular master. and are even more rare. and Challengers, are challenging the gods! they shine the brightest out of anyone. to become so good that you challenge gods, would be the most rare thing to happen.
it has nothing to do with the toughness of the mineral.. it's all about shine, gleam, and rarity.