39 examples of the new Sacagawea dollar were struck in 22 karat gold at West Point as a prelude to the Mint's eventual offering of a precious metal gold version of the "golden dollar" for collectors. A dozen of these coins went into orbit on the space shuttle Columbia on July 23, 1999 and still exist. The others were melted.
Additional information on these can be found in several articles in Coin World, Numismatic News and other media including Mike Wallace's website "United States
Small Size Dollar Coins and Related Items."
The image above is an actual gold proof and is courtesy of the U.S. Mint.