Brazilian Sapphire
Brazilian Sapphire
A persistent misnomer, a minor corundum locality, and the importance of species identification
The term Brazilian sapphire is one of the more instructive examples of trade nomenclature gone astray. In common historical and antique-trade usage, it has been applied not to corundum — the mineral species to which the name sapphire properly belongs — but to blue tourmaline mined in Brazil. The two minerals are entirely distinct: sapphire is aluminium oxide (Al₂O₃) with a Mohs hardness of 9, while tourmaline is a complex boron silicate with a hardness of 7 to 7.5. The conflation of the two, however understandable in an era before routine gemmological testing, is today considered a misnomer and is prohibited under the nomenclature standards of the International Colored Gemstone Association (ICA) and the American Gem Trade Association (AGTA). A secondary, legitimate meaning does exist: Brazil produces small quantities of genuine corundum sapphire, chiefly from alluvial deposits in the state of Mato Grosso, though output is limited and the material rarely reaches international gem markets in significant volume.
The Misnomer: Blue Tourmaline from Brazil
Brazil is among the world's foremost producers of tourmaline, and its gem-quality blue and blue-green tourmalines — particularly those from the states of Minas Gerais and Paraíba — have long attracted commercial attention. Before the widespread adoption of refractometers and other gemmological instruments in the retail trade, dealers and jewellers frequently assigned descriptive geographic-species names to stones based on colour and country of origin alone. A blue stone from Brazil could plausibly be called a "Brazilian sapphire" without any intent to deceive, simply because the vocabulary of species distinction was not yet standardised.
The practice persisted well into the twentieth century and is still encountered in antique inventories, estate jewellery appraisals, and older auction catalogues. Any piece described as containing a "Brazilian sapphire" in documentation predating approximately the 1970s should be regarded with caution and subjected to species identification before the description is accepted or repeated. The refractive index of tourmaline (typically 1.614–1.666, with strong birefringence) differs markedly from that of corundum (1.762–1.770), making identification straightforward with a refractometer.
It is worth noting that blue tourmaline from Brazil is itself a valuable and legitimate gemstone. The extraordinary neon-blue and blue-green Paraíba tourmaline, discovered in the late 1980s in the state of Paraíba and subsequently found in Rio Grande do Norte, commands among the highest per-carat prices of any tourmaline in the world, owing to its copper-and-manganese chromophores and exceptional saturation. Calling such a stone a "sapphire" of any kind does it no commercial favour in the modern market; its correct identity is both more accurate and, in the case of fine Paraíba material, more commercially advantageous.
Nomenclature Standards and Trade Prohibitions
Modern gem-trade nomenclature bodies are explicit on this point. The AGTA's nomenclature guidelines prohibit the use of one gem species name for another, regardless of colour similarity or geographic association. The ICA similarly requires that trade names not mislead consumers as to the identity of a stone. Under these standards, "Brazilian sapphire" is permissible only when referring to genuine corundum of Brazilian origin; applied to tourmaline, it constitutes a prohibited misnomer.
The broader category of such misnomers — geographic or colour-based names that assign one species' identity to another — includes terms such as "Cape ruby" (for pyrope garnet), "Bohemian ruby" (also garnet), and "Oriental emerald" (for green corundum, i.e., green sapphire). All persist in antique contexts and all require the same corrective approach: species identification followed by accurate re-labelling.
True Brazilian Corundum: The Mato Grosso Deposits
Brazil is not, in the strict sense, a sapphire country of any commercial significance, but genuine corundum sapphire has been recovered from alluvial deposits in the state of Mato Grosso, in the west-central interior of the country. The deposits are associated with weathered metamorphic and igneous terrains, and stones are recovered by artisanal methods from river gravels and eluvial soils.
The material from Mato Grosso is variable in quality. Colours range from pale to medium blue, with some yellowish or greyish modifiers that reduce desirability. Strongly saturated, clean blue stones of significant carat weight are uncommon. The deposit has not attracted the sustained commercial development seen at major sapphire localities such as Mogok (Myanmar), Ratnapura (Sri Lanka), Ilakaka (Madagascar), or the Anakie fields of Queensland (Australia), and Brazilian sapphire rarely appears as a named origin in major auction catalogues or laboratory origin reports.
Gemmological laboratories such as the Gübelin Gem Lab, SSEF, and GIA's Gem Laboratory do issue origin determinations for corundum, but Brazilian origin for sapphire is not among the commonly documented provenance designations, reflecting the rarity of fine material from the country. A sapphire correctly identified as being of Brazilian corundum origin carries no particular premium in the current market; it is valued on its individual merits of colour, clarity, and cut rather than on any origin-based reputation.
Identifying the Stone: Practical Gemmology
For a gemmologist or appraiser encountering a stone described as a "Brazilian sapphire," the first task is unambiguous species identification. Key distinguishing properties are as follows:
- Refractive index: Corundum reads 1.762–1.770 (birefringence 0.008–0.009); tourmaline reads approximately 1.614–1.666 (birefringence 0.014–0.021, occasionally higher in some varieties).
- Specific gravity: Corundum, approximately 3.99–4.01; tourmaline, approximately 3.00–3.26 depending on composition.
- Crystal system: Corundum is trigonal with a characteristic hexagonal habit and parting; tourmaline is also trigonal but with a distinctly striated prismatic habit and hemimorphic terminations.
- Pleochroism: Blue sapphire shows moderate to strong pleochroism (blue to blue-green or violet); blue tourmaline also shows pleochroism, but the colours and intensities differ and the birefringence is more pronounced under the polariscope.
- Inclusions: Corundum typically shows silk (rutile needles), fingerprints, and growth zoning; tourmaline shows characteristic parallel growth tubes, irregular fractures, and sometimes colour zoning perpendicular to the c-axis.
Advanced testing — including laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) trace-element analysis — can confirm species and, for corundum, assist in origin determination, though this level of analysis is typically reserved for stones of significant value.
In the Trade and in Antique Contexts
Dealers in antique and estate jewellery will continue to encounter the term "Brazilian sapphire" in old invoices, insurance schedules, and auction records. The responsible course is to treat the description as a starting point for investigation rather than a conclusion. Where the stone proves to be tourmaline, the description should be corrected in any new documentation; where it proves to be genuine corundum of Brazilian origin, the description is technically accurate but should be supplemented with species confirmation.
The persistence of such misnomers in the historical record is itself of documentary interest, offering a window into the commercial and scientific practices of earlier periods. It does not, however, justify their perpetuation in contemporary trade documents, appraisals, or laboratory reports.