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 customs by country weddings in the United States follow a similar pattern to an English wedding. It traditionally follows the "white wedding" type (see also "Wedding types" below), which originates from the white color of the bride's wedding dress, but refers to an entire wedding routine. Customs and traditions vary, but common components are listed below. The purpose of inviting guests is to have them witness a couple's marriage ceremony and vows and to share in their joy and celebration. Gifts for the wedding couple are optional, although most guests attempt to give at least a token gift of their best wishes. Some