The yellow to golden variety of quartz, colored by trace elements of iron, is named citrine. The color of citrine closely resembles the color of – the more expensive – yellow topaz and consequently citrine is sometimes marketed under various misnomers such as Madeira topaz , Bahia topaz, and topaz quartz. Today, citrine is often actually the more abundant amethyst which has been heated to a temperature of approximately 900 degrees Fahrenheit (ca. 450 to 480 degrees C.). This creates a stable golden to yellow color which can be restored to its original color upon irradiation. Citrine is the second most coveted variety of quartz after amethyst.