What do you mean,"What is opal stone more durible"?
Very
yes there is.. its called opal royal or morado opal.. indeed its true
You get them by digging in the underground. It looks like a long smooth rock.
Yes, it is often set with pearls or diamonds and was used extensively in Victorian and Edwardian jewellery.
No Rubies are generally not as expensive as diamonds, but it depends on the quality, size, and the supply and the demand.