Minerals & Crystals Codexery

Spinel

A gemstone mineral often mistaken for ruby.

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Pointed crystal shapes gave spinel its name, which derives from the Latin term spinella, a shortened form of the word for spine.[1]

Key facts and history

Chromium(III) causes the red color in spinel from Myanmar, according to a Caltech source.[2][3] Some spinels are among the most famous gemstones, including the Black Prince's Ruby and the Timur Ruby in the British Crown Jewels.[4] Transparent red spinels were historically called spinel-rubies or balas rubies, with "Balas" deriving from Balascia, the ancient name for Badakhshan.[5] In the isometric crystal system, spinel typically forms twinned octahedral crystals.[6]

With a hardness rating of 8 and a specific gravity between 3.5 and 4.1, spinel exhibits conchoidal fracture and octahedral parting rather than true cleavage.[6] For many centuries, the primary source of red and pink spinels was mines located in the Gorno Badakhshan area of what is now Tajikistan.[7] Metamorphic spinel occurs in metamorphosed limestones and mudstones that are low in silica.[8]

What the research sources say

The same source states that spinel provides better protection in hostile environments and can withstand sand and rain erosion.[9] According to the Phys.org article, spinel has unique optical properties, allowing infrared light to pass through it.[9] The Wondermondo account notes that cobalt blue spinel from Lục Yên, Vietnam, was discovered in the early 2000s and remains very rare and increasingly expensive.[10] The same source reports that since 2015, a technology to color greyish spinels vivid blue with cobalt diffusion treatment has been noticed.[10]

References

  1. Wikipedia, "Spinel" (CC BY-SA 4.0) en.wikipedia.org
  2. "Minerals colored by metal ions", minerals.gps.caltech.edu. facts only, no text reused. minerals.gps.caltech.edu
  3. Wikipedia, "Spinel" (CC BY-SA 4.0), which cites: Klein, "Manual of Mineralogy (after James D. Dana)", Wiley, 1993; "Minerals colored by metal ions", minerals.gps.caltech.edu (we also read that source) en.wikipedia.org
  4. Wikipedia, "Spinel" (CC BY-SA 4.0), which cites: Sir Thomas Butler, "The Crown Jewels and Coronation Ceremony", Pitkin, 1989, p. 6; Pardieu, "Spinel from Tajikistan", InColor, Summer 2019, p. 30–33; "Samarian spinel", Dictionary of Gems and Gemology, 2005, p. 657–737 (original not read by us) en.wikipedia.org
  5. Wikipedia, "Spinel" (CC BY-SA 4.0), which cites: Lytvynov, "On the words used as names for ruby and sapphire", Functional Materials, 2011, p. 275; Hughes, "The rubies and spinels of Afghanistan: A brief history", Journal of Gemmology, 1994, p. 256–267; Pardieu Farkhodova 2019 (original not read by us) en.wikipedia.org
  6. Wikipedia, "Spinel" (CC BY-SA 4.0), which cites: Nesse, "Introduction to mineralogy", Oxford University Press, 2000, p. 362–363 (we also read that source) en.wikipedia.org
  7. Wikipedia, "Spinel" (CC BY-SA 4.0), which cites: Biswas, "Metallurgy in India : a retrospective", India International Publisher, 2001, p. 1–22; Pardieu Farkhodova 2019 (original not read by us) en.wikipedia.org
  8. Wikipedia, "Spinel" (CC BY-SA 4.0), which cites: Klein, "Manual of Mineralogy (after James D. Dana)", Wiley, 1993 (we also read that source) en.wikipedia.org
  9. "Researchers finding applications for tough spinel ceramic", Phys.org, 24 April 2015. facts only, no text reused. phys.org
  10. Wondermondo, "Finds of cobalt blue spinel in Lục Yên, Vietnam", 16 June 2019. facts only, no text reused. wondermondo.com

Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Spinel (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.

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Sources

Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.

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