Niobium, formerly sometimes called Columbium in the United States.

Niobium Medal by Wah Chang, 2004. Diameter 39mm, .999 pure. $30 on 4/26/2006.
The Wah Chang Company of Albany OR (also known as ATI Wah Chang and Teledyne Wah Chang) specializes in fabricating parts for the nuclear industry out of exotic metals such as niobium, zirconium, hafnium, tantalum, titanium and vanadium. The niobium medal pictured above is one of the three available through their website. This one commemorates the first rocket-powered flight, by Fritz von Opel. It is very well made, and a nice big chunk of niobium.
Niobium medal by Metallium, Inc. Photo used by permission.
Diameter 19 mm, 3.7 grams, 99.9% pure. $14 on 6/9/2006.
Although no circulating legal tender coins made purely out of niobium, Austria has produced several bimetallic 25 euro coins with a silver ring and a niobium center which is anodized various colors. One official distributor is EuroCollections International. The coin below is not in my collection.
