Labradorite – Natural, Cabochon, Blue

Most labradorite shows parallel lines due to its twinning planes. However, some specimens show a pattern that can look like crazing and potch in a precious opal. "Gemstone Collection - Labradorite," photo by Marco Hazard. Licensed under CC By-SA 2.0.

Article: Opal Simulants: How to Spot Imitation Opal

Credit: Marco Hazard