Chrysoberyl

Chrysoberyl, a captivating gemstone with a name rooted in Greek, combines "chrysos" meaning golden and "beryllos" signifying a type of precious stone. This aptly named gemstone is renowned for its lustrous brilliance and remarkable durability.

Chemically composed of beryllium aluminium oxide, chrysoberyl is distinct from other beryl gemstones like emerald and aquamarine. Its striking green or yellow hues, characterized by exceptional clarity, have made it a cherished choice in jewellery for centuries.

Chrysoberyl's geological origins can be traced to metamorphic rocks and alluvial deposits, with notable sources including Brazil, Sri Lanka, and Madagascar. Its resilience, often compared to sapphire, has earned it a reputation as one of the world's hardest gemstones.

One of the most fascinating features of chrysoberyl is its unique optical phenomenon known as cat's-eye or chatoyancy, where a luminous band appears to glide across the surface when the gemstone is cut en cabochon. This captivating effect adds to the gem's allure and continues to captivate gemstone enthusiasts and collectors alike.

Click on the terms in the table below to discover their meaning

Image of star form Yellow Chrysoberyl — Star form Yellow Chrysoberyl by Mateo Chinellato (used under CC BY-SA 3.0 licence)

Image of Cat's Eye Chrysoberyl — Cat's Eye Chrysoberyl by Chip Clark (used under CC0 1.0 licence)

Image of Alexandrite variety of Chrysoberyl showing colour change under different lighting conditions — Alexandrite variety of Chrysoberyl showing colour change under different lighting conditions by David Weinberg (used under CC BY-SA 3.0 licence)

Click on the terms in the table below to discover their meaning

Name	Chrysoberyl
Category	Oxide mineral (Spinel group)
Chemical Formula	BeAl₂O₄
Chemical Formula
IMA Symbol	Cbrl
Crystal System	Orthorhombic
Crystal Habit	Tabular or short prismatic; prominently striated
Twinning	Common, producing either flattened heart-shaped or pseudohexagonal multiple contact and penetration twins
Cleavage	Good / Distinct
Fracture	Conchoidal to uneven
Tenacity	Brittle
Hardness (Moh's Scale)	8.5
Specific Gravity	3.69 - 3.75
Diaphaneity	Transparent to translucent, may be opaque and display chatoyancy with oriented inclusions
Colour	Green, yellow, brown, greenish black, may be raspberry-red under incandescent light when it contains chromium; colourless, pale shades of yellow, green, or red in transmitted light
Streak	White
Lustre	Vitreous
Optical Class	Biaxial (+)
Refractive index	nα = 1.745
	nβ = 1.748
	nγ = 1.754
Birefringence	δ = 0.010
Dispersion	Rd = 0.014
Pleochroism	Very weak


Clarity	Type I
Notable Varieties	Yellow Chrysoberyl, Green Chrysoberyl, Alexandrite, Cat's Eye Chrysoberyl

References

Mineralogical Society of America. (2005). Chrysoberyl. In J. W. Anthony, R. A. Bideaux, K. W. Bladh, & M. C. Nichols (Eds.), Handbook of Mineralogy. Chantilly, VA 20151-1110, USA: Mineralogical Society of America. Retrieved from https://www.handbookofmineralogy.org/pdfs/chrysoberyl.pdf

The Gemology Project. (2012, August 13). Chrysoberyl. Retrieved from The Gemology Project: http://gemologyproject.com/wiki/index.php?title=Chrysoberyl

About the Author

Daniel Gillespie is student of Web Development and the developer of Gemology 101. With a straightforward and informative approach, Daniel invites readers to explore the world of gemology, offering a valuable resource for both enthusiasts and those seeking knowledge about precious stones.