Crystal structure "white tin" respectively. Two more allotropes, γ and σ, exist at temperatures above 161 °C and pressures above several GPa. White tin is metallic, and is the stable crystalline form at or above room temperature. Below 13.2 °C, tin exists in the gray form, which has a diamond cubic crystal structure, similar to diamond, silicon or germanium. Gray tin has no metallic properties at all, is a dull gray powdery material, and has few uses, other than a few specialized semiconductor applications. Although the α–β transformation temperature of tin is nominally 13.2 °C, impurities (e.g. Al, Zn, etc.) lower the
Puyo Puyo! 15th Anniversary Puyo Puyo! 15th Anniversary Ms. Accord, the teacher at the Primp Magic School, informs Sig that there will be a tournament up for play, and everyone's competing; the reward is a medal that will grant anyone's single wish. Another scene shows Amitie and Arle pledging to play by the rules, and Sig, still as clueless as ever, eventually plegdes as well, but not before witnessing six comets fall down onto Earth. Sig, realising that this is a big discovery, decides to ignore it anyhow and goes onto the competition. It turns out that the "comets" are actually six familiar characters