Tin medal by Metallium, Inc. Photo used by permission.
Diameter 19 mm, 3.1 grams, 99.9% pure. $7 on 7/6/2006.
Tin (Latin stannum) has been known since ancient times. Tin is typically alloyed with other metals for coins. Thailand is one of the few countries that has made coins out of pure tin. There is an interesting reason why pure tin coins aren't often seen.
Tin has two allotropic forms, or arrangements of atoms in its crystal structure. White tin, the ordinary form of the metal, exists above 13.2 degrees C (55.7 degrees Fahrenheit). Below that temperature, it slowly changes to Gray tin, which is a crumbly powder. This phenomenon is called "tin pest" and was first noticed on organ pipes in drafty European cathedrals which got cold in the wintertime.
Presumably Thailand, being a tropical paradise, doesn't have to worry about tin pest. Numismatists living in Alaska may want to keep their tin coins in a warm place.
Tin medal by Metallium, Inc. Photo used by permission.
Diameter 19 mm, 3.1 grams, 99.9% pure. $7 on 7/6/2006.