Natural Spinel Colours: Chromium, Iron and Cobalt Explained

Spinel is more than a red gemstone. Natural examples can be pink, violet, blue and many other shades. Its colour range reflects small differences in chemistry, while its crystal shape and geological setting add further interest for collectors.

The role of colour-producing elements

SSEF’s 2011 overview describes chemically pure spinel as colourless. Chromium can contribute pink and red, while iron, vanadium and occasionally cobalt influence other colours. The mix and amounts matter, so there is no single colour for all spinel.

The article discusses classic and newer sources, including Myanmar, Sri Lanka, Tajikistan, Vietnam, Madagascar and Tanzania. These are historical source examples, not a complete list of every occurrence.

Crystal shape is another clue

Spinel has a cubic crystal structure and commonly forms octahedra, which resemble two pyramids joined at their bases. Twinning can create interesting shapes. A rough crystal can therefore be attractive even before it is faceted.

Avoid two common assumptions

A country cannot be proved from colour alone, and the word spinel does not by itself prove that a stone is natural or untreated. Those questions need their own evidence. SSEF’s article explains that origin assessment requires enough microscopic, chemical and spectroscopic support. Enjoy the colour as an individual quality of the gem, while reading formation, treatment and origin statements separately.

Sources and further reading

SSEF Swiss Gemmological Institute, Facette, issue 18, January 2011, pp. 3-4, “Spinel, a gemstone on the rise”. Read the original SSEF PDF.

This independent educational article explains historical SSEF research in original, simple English. It is not an SSEF publication. No source photographs or illustrations are reproduced.