spinel

Spinel, a captivating gemstone, takes its name from the Latin word "spinella," meaning "little thorn" or "spark." Composed of magnesium aluminium oxide, spinel boasts a brilliant range of colours, from deep reds and blues to vibrant pinks and purples.

Spinel's geological origins are closely associated with marble and limestone formations, often occurring as octahedral crystals within these rocks. Notable sources include Myanmar, Sri Lanka, and Tanzania.

What sets spinel apart is its exceptional hardness and durability, ranking 8 on the Mohs scale, making it a superb choice for jewellery. Throughout history, spinel has often been mistaken for other gemstones, including rubies and sapphires, due to its vivid colours.

One fascinating fact about spinel is its use in royal jewellery, including the "Black Prince's Ruby" in the British Imperial State Crown. This gemstone's rich history, stunning colours, and impressive properties continue to make it a highly sought-after and cherished gem in the world of fine jewellery and gemology.

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

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

Name Spinel
Category Oxide mineral (Spinel group)
Chemical Formula MgAl2O4
IMA Symbol Spl
Crystal System Cubic (Isometric)
Crystal Habit Commonly as octahedra, may show dodecahedron or cube faces, rarely as dodecahedra; coarse granular, rounded, massive
Twinning Common as penetration or contact twins; may be repeated as sixlings
Cleavage None
Fracture Conchoidal to uneven
Tenacity Brittle
Hardness
(Moh's Scale)		 7.5 - 8
Specific Gravity 3.6 - 4.1
Diaphaneity Transparent to nearly opaque
Colour Colourless, yellow, orange, red, pink, violet, indigo, blue, green, brown, grey, black
Streak White
Lustre Vitreous
Optical Class Isotropic
Refractive index n = 1.719
Birefringence Absent
Dispersion Rd = 0.020
Pleochroism Absent
Clarity Type II
Notable Varieties Red Spinel, Colour-change Spinel, Star Spinel (displays asterism), Mahenge Spinel, Burmese Spinel, Tajikite (Tajik Spinel)

References

Hudson Institute of Mineralogy. (2023). Spinel. Retrieved from Mindat.org: https://www.mindat.org/min-3729.html

Mineralogical Society of America. (2021). Spinel. 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/Spinel.pdf

The Gemology Project. (2012, August 17). Spinel. Retrieved from The Gemology Project: http://gemologyproject.com/wiki/index.php?title=Spinel

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.