Tin pest related problems such as tin whiskers. At 13.2 °C (about 56 °F) and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form "white tin" to the brittle, nonmetallic, α-form "grey tin" with a diamond cubic structure. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures of roughly −30 °C aids the initiation. There is also a large volume increase of about 27% associated with the phase change to the nonmetallic low temperature allotrope. This frequently makes tin
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