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
Gift economy Gift economy A gift economy, gift culture, or gift exchange is a mode of exchange where valuables are not traded or sold, but rather given without an explicit agreement for immediate or future rewards. This exchange contrasts with a barter economy or a market economy, where goods and services are primarily exchanged for value received. Social norms and custom govern gift exchange. Gifts are not given in an explicit exchange of goods or services for money or some other commodity. The nature of gift economies forms the subject of a foundational debate in anthropology. Anthropological research into gift economies began