Their inclusions of undissolved flux can look like inclusions in natural chrysoberyl. Brazilianite is often confused with amblygonite, apatite, chrysoberyl, beryl, and topaz. Associated mineral include fluorite, liberite, chrysoberyl, taaffeite and nigerite. The color in yellow chrysoberyl is due to Fe impurities. Translucent yellowish chatoyant chrysoberyl is called cymophane or cat's eye. This unusual requirement explains the rarity of this chrysoberyl variety. Colour change is most commonly found in alexandrite, a variety of chrysoberyl gemstones. Gem minerals include amethyst, chrysoberyl, brazilianite, topaz and quartz. Anderson "et al.", classified taaffeite as an intermediate mineral between spinel and chrysoberyl. If the pegmatite fluid is rich in beryllium, crystals of beryl or chrysoberyl could form. Gem species known for this phenomenon include the aforementioned quartz, chrysoberyl, beryl (especially var. Ordinary chrysoberyl is yellowish-green and transparent to translucent. Notable gemstones which contain beryllium include beryl (aquamarine, emerald) and chrysoberyl. An alexandrite cat's eye is a chrysoberyl cat's eye that changes color. Rutile, aragonite, cerussite, and chrysoberyl often exhibit cyclic twinning, typically in a radiating pattern.