Chrysoberyl

Chrysoberyl is a beryllium aluminum oxide mineral, BeAl₂O₄, prized as a gemstone. Its notable varieties include color-changing alexandrite and chatoyant cat’s eye.

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Beryllium: Beryllium is a lightweight alkaline-earth metal and a component of several minerals and alloys. Beryllium is one of the two cations in chrysoberyl’s chemical formula.
Alexandrite: Alexandrite is a chromium-bearing variety of chrysoberyl that changes from greenish hues in daylight to reddish hues under incandescent light. Its chromium absorption creates chrysoberyl’s celebrated daylight-to-lamplight color change.
Alexandrite effect: The alexandrite effect is a marked color change between daylight-like and incandescent illumination in certain gemstones. This effect names the signature optical behavior of alexandrite chrysoberyl.
Corundum: Corundum is crystalline aluminum oxide, occurring as ruby and sapphire when colored by trace elements. Corundum is another durable gemstone, but it contains no beryllium and has a different crystal structure.
Aluminum oxide: Aluminum oxide is a chemical compound found naturally as corundum and used in ceramics and abrasives. Aluminum and oxygen form the framework of chrysoberyl’s oxide structure.
Cat’s-eye chrysoberyl: Cat’s-eye chrysoberyl is a chrysoberyl variety whose aligned inclusions produce a sharp band of reflected light. Its chatoyant band is the defining optical feature of this chrysoberyl variety.
Cat’s-eye effect: The cat’s-eye effect is a narrow band of reflected light that moves across a cabochon gemstone. Chrysoberyl is the classic gem material exhibiting this form of chatoyancy.
Beryl: Beryl is a beryllium aluminum silicate mineral that includes emerald and aquamarine. Despite sharing beryllium and aluminum, beryl is a silicate rather than an oxide.
Orthorhombic crystal system: The orthorhombic crystal system has three mutually perpendicular axes of unequal length. Chrysoberyl crystals belong to this system, shaping their symmetry and crystal habits.
Chromium: Chromium is a chemical element whose ions color minerals and enable ruby’s fluorescence. Chromium substitutes into alexandrite’s crystal lattice and selectively absorbs light.