Tin bent, a crackling sound known as the "tin cry" can be heard from the twinning of the crystals. Tin melts at low temperatures of about , the lowest in group 14. The melting point is further lowered to for 11 nm particles. β-tin (the metallic form, or white tin, BCT structure), which is stable at and above room temperature, is malleable. In contrast, α-tin (nonmetallic form, or gray tin), which is stable below , is brittle. α-tin has a diamond cubic crystal structure, similar to diamond, silicon or germanium. α-tin has no metallic properties at all because its atoms form
Anniversary to as the "traditional" list. Generally speaking, the longer the period, the more precious or durable the material associated with it. See wedding anniversary for a general list of the wedding anniversary symbols; however, there are variations in some national traditions. Furthermore, there exist numerous partially overlapping, partially contradictory lists of anniversary gifts (such as wedding stones), separate from the 'traditional' names. The concepts of a person's birthday stone and zodiac stone, by contrast, are fixed for life according to the day of the week, month, or astrological sign corresponding to the recipient's birthday. Anniversary An anniversary is the date