There may not be a pot of gold at the end of the rainbow, but there appears to be nanocrystalline diamonds at the end of a process to produce and store hydrogen using Anthracite coal, according to a recent report from azonano.com:

Interest in hydrogen as a vehicular fuel has many researchers investigating ways to create hydrogen inexpensively; other researchers are looking at ways to transport and store hydrogen in a safe manner. Penn State Assistant Professor Angela D. Lueking and her group were exploring a way to store hydrogen in carbon-based materials, and inadvertently stumbled upon a method that combines production and storage and produces nanocrystalline diamonds as a by-product.

What the researchers had were bucky diamonds, a nanocrystalline diamond surrounded by onion-like layers of graphite.

"Bucky diamonds are relatively unexplored in terms of applications," said Lueking. "Nanocrystalline diamonds, however, have major industrial uses as abrasives and in electronics." (photo NCSU)