- Opals flash beautiful colours as you turn the stone or move around it. This phenomenon is called play-of-colour. An opal might show a single colour, two or three colours, or an entire rainbow.
- Opal is the birthstone for the month of October.
- The best play-of-colour is the brightest; an opal displaying a full rainbow is the most rare and valuable.
- Opals are known by their background colours and are called "black," "white," "gray," or "fire" opals.
- Once the rough opal is cut and polished, the play-of-colour will be brightest.
- Opals rate 5.5 to 6.5 on the mohs hardness scale, and require special care when worn in jewellery.
July 10, 2014
by Perrine Comeille
