Lets think about some basic questions
Is opal a gemstone?
How is opal formed?
What gives opal colour?
Can opal be more expensive than diamond?
Are opals found outside of Australia?
Can opals be found in sedimentary rocks?
Can opals be found igneous rocks?
Is opal harder than diamond?
Is opal harder than quartz?
Is there such a thing as synthetic opal?
What is synthetic opal?