CHRYSOBERYL

 Chrysoberyl is a beryllium aluminum oxide mineral that includes several gemstone varieties. The most well-known and significant varieties of chrysoberyl are Alexenderite, Yellow Chrysoberyl, and Cat's Eye Chrysoberyl, in general, these gemstones are known for their durability, excellent hardness (8.5 on the Mohs scale), and brilliance. They are suitable for various types of jewelry and are appreciated for their unique optical effects. The cat's eye chrysoberyl, in particular, is sought after for its intriguing chatoyancy.
Alexandrite is a remarkable and highly prized variety of chrysoberyl that is known for its unique colour-changing properties. In daylight or fluorescent light, it appears green to bluish-green colour, while under incandescent light, it exhibits a reddish-purple to purplish-red hue. This phenomenon is known as the alexandrite effect. Alexandrite is one of the rarest and most valuable gemstones.
Cat's Eye variety of chrysoberyl is known for its distinct chatoyancy or cat's eye effect. When cut as a cabochon, a band of light moves across the surface, resembling the slit eye of a cat. The cat's eye effect is caused by needle-like inclusions of rutile or other minerals. Cat's eye chrysoberyl can come in various colours, with green and yellow being common.

Yellow chrysoberyl is the most common variety of chrysoberyl. It can range in colour from yellowish-green to brownish-yellow. While it may not be as well-known as alexandrite, it is valued for its hardness, brilliance, and attractive colors.
Chrysoberyl deposits are found in various locations around the world, with notable sources including Brazil, Sri Lanka, Russia, Madagascar, and Tanzania. When considering chrysoberyl gemstones, the quality factors include colour, clarity, cut, and the presence of special optical phenomena like colour change or cat's eye effect, which significantly affect their value.