Smoky quartz is a light to dark yellowish brown to orange brown. The finest smoky quartz will display flashes of orange and brown. Smoky quartz gets its color from natural radiation interacting with aluminum in the crysatal. Colorless quartz is sometimes irradiated to turn it into smoky quartz. Smoky quartz is sometimes heat treated to make it a greenish yellow that resembles citrine. Many people often confuse smoky quartz with topaz do to their similar appearance. However smoky quartz is a fraction of the price of topaz, and is often used as an alternative in jewelry.