This is a beautiful man-made gemstone that's also known as Imori Stone, after its creator.
It was made in the 1960s at Imori Labortory Ltd. in Tokyo, Japan. Dr. Imori blended powdered natural minerals and other secret ingredients, melted them together and cooled them in a secret process for several months. The result was material displaying a fascinating shimmering appearance in a wide range of colors.
When Dr. Imori passed away it was discovered that Imori Stone's secret formula died with him -- it was never written down. There have been many attempts to duplicate his process but none have been successful so far. Production ended in 1985 so the current supply is very limited.