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
Wedding ring Wedding ring A wedding ring or wedding band is a finger ring that indicates that its wearer is married. It is usually forged from metal, and traditionally is forged of gold or another precious metal. The earliest examples of wedding rings are from Ancient Egypt. Western customs for wedding rings can be traced to ancient Rome and Greece, and were transmitted to the present through Christendom in Europe, which adapted the ancient customs. Depending on culture, a wedding ring is typically worn on the base of the left or right ring finger, if the wearer is left handed often it