Citrine belongs to the quartz family and is composed primarily of silica (SiO2). It ranges in color from pale yellow to very dark orange. The color is caused by inclusion of colloida iron hydrates. A deep golden, dark orange color is produced when the citrine crystals formed at very high temperatures. Citrine is widely used as a gemstone for faceting and jewelry making. It sometimes is mistaken for topaz, a more expensive gemstone. Citrine is found lining the walls inside cavities in volcanic rock.