Fire. Black opals are the most valuable opals in the world. The most beautiful examples of these come from the Lightning Ridge mining area in Australia. Opals are classified according to the pattern of the fire within the stone. This example is a cross between pinfire and palette. While some lists show that Tourmaline or Pink Zircon is the gemstone for those who were born in October, opal is actually the traditional stone. Now days, Tourmaline is said to be an alternative. I think that came about because they come in so many different colors. I don‘t know who came up with Pink Zircon, but it was hugely popular when I was a kid as THE stone for October birthdays. Personally, I never considered it valid.