Opal, meaning "precious stone" of which there are many different types with different energetic properties.
Common Opal is generally opaque and doesn't exhibit the light reflecting properties that some of the other Opals do, coming in white, pink, blue or brown or black. these common Opals vibrates at a lower frequency and are gentler in intensity making them more calming and soothing than some other stones that can be overbearing to some.
Precious Opals, such as white, (most commonly used in jewelry) and black, are filled with a seemingly iridescent "fire" and are excellent amplifiers of emotion.
*Gemstone information gathered from "The Book of Stones" by Robert Simmons and Naisha Ahsian. Pick this book up for an in-depth description of almost every stone on Earth!