Almandine Spinel
Almandine Spinel
An obsolete trade name for violet-red and purplish-red spinel, now retired from modern gemmological usage
Almandine spinel is a historical trade designation applied to spinel specimens displaying a violet-red or purplish-red colour broadly reminiscent of almandine garnet. The term was in common use during the nineteenth and early twentieth centuries, when gem nomenclature was frequently organised around visual resemblance rather than mineralogical identity. It has since been abandoned by modern gemmology: neither the Gemological Institute of America nor any major gemmological laboratory employs the designation today, and stones formerly described by this name are now identified simply as spinel, with colour characterised as violet, purplish-red, or red according to standardised grading language.
Origin of the Name
The term arose from a straightforward, if scientifically imprecise, colour analogy. Almandine garnet — the iron-aluminium member of the garnet group — commonly occurs in deep reddish-violet to purplish-red tones. Spinel of similar hue was accordingly labelled "almandine spinel" by dealers and jewellers who wished to communicate colour character to buyers unfamiliar with the distinction between the two minerals. The naming convention was not unique to spinel: the same era produced "rubicelle" for orange-red spinel, "balas ruby" for pale rose-red spinel, and "sapphirine" for blue spinel — all colour-descriptive terms that conflated appearance with identity and, in several cases, implied an erroneous relationship to ruby or sapphire.
Almandine garnet and spinel are mineralogically unrelated. Almandine belongs to the nesosilicate garnet supergroup, with the general formula Fe3Al2(SiO4)3, while spinel is a magnesium aluminium oxide (MgAl2O4) belonging to the spinel group of oxides. Their shared colour range in the violet-red region is coincidental, arising from different chromophoric mechanisms: iron and manganese in almandine, and varying combinations of iron, chromium, and vanadium in spinel.
Gemmological Character of the Stones So Described
The spinels historically sold under the almandine designation occupy the cooler, more violet end of the red spinel spectrum. In modern colour description, such stones would be graded as strongly purplish-red to violet-red, distinguishable from the warmer, more chromium-dominant reds associated with Burmese "pigeon's blood" ruby-like spinels. The violet character in these stones is typically attributed to elevated iron content relative to chromium, which shifts the dominant hue away from pure red toward the blue-violet region of the spectrum.
Physically, these stones share all the properties of spinel: isometric crystal system, hardness of 8 on the Mohs scale, refractive index of approximately 1.718, and single refraction — the last being one of the most reliable diagnostic features separating spinel from the doubly refractive almandine garnet. Specific gravity is approximately 3.60. Under the Chelsea colour filter, iron-rich violet spinels typically show no reaction or a weak red, unlike chromium-rich red spinels, which fluoresce more strongly.
Historical Usage and Antique Jewellery
The term almandine spinel appears in nineteenth-century gem trade catalogues, auction records, and jewellery inventories, particularly in British and Continental European contexts. Collectors and curators working with Georgian and early Victorian jewellery may encounter the designation in original documentation, hallmark records, or estate inventories. In such contexts, the term should be understood as a colour descriptor of its era rather than a mineralogical classification. Reidentification of stones described as almandine spinel in antique pieces is straightforward by standard gemmological testing, principally refractive index measurement and specific gravity determination, which unambiguously separate spinel from garnet.
It is worth noting that misidentification was not merely a matter of nomenclature: some stones sold as almandine spinel in the antique trade may in fact be almandine garnet, and vice versa, given that the original labelling was based on colour alone. Laboratory testing of stones from antique settings described by this term is therefore advisable before any significant valuation or insurance assessment.
Retirement from Modern Nomenclature
The systematic rationalisation of gem nomenclature through the twentieth century, driven principally by the GIA, the International Coloured Gemstone Association (ICA), and national gemmological associations, eliminated colour-analogy trade names in favour of species and variety designations grounded in mineralogy. Under this framework, all members of the spinel group are identified as spinel, with colour described separately using standardised hue, tone, and saturation language. The term almandine spinel does not appear in GIA laboratory reports, ICA guidelines, or the nomenclature systems of SSEF, Gübelin, or Lotus Gemology.
The term persists today only in three contexts: antique jewellery descriptions and auction catalogue notes referencing historical documentation; academic and historical literature on the evolution of gem trade nomenclature; and, occasionally, in the secondary market for estate jewellery where original period descriptions are preserved for provenance purposes. In all contemporary gemmological writing, the preferred designation is simply spinel, qualified by colour as appropriate.
Significance for Collectors and Researchers
Understanding obsolete trade names such as almandine spinel is of practical value to collectors of antique jewellery, auction specialists, and museum curators. A working knowledge of historical nomenclature allows accurate interpretation of period documents, prevents confusion between colour-analogy names and true mineralogical identities, and supports informed attribution when stones cannot be removed from their settings for testing. The broader family of obsolete spinel trade names — balas ruby, rubicelle, almandine spinel, sapphirine — constitutes a coherent historical record of how colour perception, rather than crystal chemistry, once organised the gem trade, and remains a legitimate subject of gemmological history.