Moonstone, a moderately hard, transparent or translucent gemstone with a pearly or milky luster. Moonstone is a feldspar, either orthoclase (potassium aluminum silicate) or albite (sodium aluminum silicate). The stone is found in all continents except Africa; the best specimens are mined in Sri Lanka. It is the birthstone for June and represents health.
Every day, astronomers unravel a little more of the universe's inner workings, but the jury is still out on 95 percent of its contents.
He is famous for a phrase he never said, for wearing turtlenecks and for hosting the original 'Cosmos' TV series. As enthusiastic about the stars as he was about marijuana, Carl Sagan led a very surprising life. Here are 10 cool facts.