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
Wedding anniversary widely marked as her Diamond Jubilee. The origins of the current gift conventions date to 1937. Before that, only the 1st, 5th, 10th, 15th, 20th, 25th, 50th, and 75th anniversaries had an associated gift. In 1937, the American National Retail Jeweler Association (now known as Jewelers of America as a result of an organizational merger) introduced an expanded list of gifts. The revamped list gave a gift for each year up to the 25th, and then for every fifth anniversary after that. Lists of wedding anniversary gifts vary by country. The traditional and modern U.S. versions were compiled by librarians