Brazilian alexandrite is colour-change chrysoberyl (BeAl₂O₄) mined primarily in the state of Minas Gerais, Brazil, and represents the most commercially significant source of alexandrite in the world today. First recovered in meaningful quantities during the 1980s, Brazilian material rapidly filled the supply vacuum left by the near-exhaustion of the historic Russian deposits in the Ural Mountains. While the colour shift in Brazilian stones is generally less dramatic than that of the finest Russian examples, exceptional specimens from Brazil exhibit vivid, well-saturated changes and have commanded substantial prices at auction and in the trade. The deposits are notable for yielding crystals of considerable size, making faceted stones above one carat — a rarity in alexandrite overall — comparatively accessible from Brazilian sources.

Geological Setting and Principal Deposits

The alexandrite-bearing geology of Minas Gerais is associated with Precambrian metamorphic terranes, specifically with emerald- and chrysoberyl-bearing pegmatites and schists that intrude or border ultramafic rocks. The chromium responsible for alexandrite's colour-change phenomenon is derived from the surrounding country rock and introduced into the crystallising beryllium-aluminium oxide during metamorphic or pegmatitic events.

The two most important localities are:

• Hematita — a municipality in the southern portion of Minas Gerais, historically the most prolific single source of Brazilian alexandrite. Stones from Hematita are sometimes identified in the trade under the locality name itself, occasionally appearing as Hematita alexandrite. The deposit was intensively worked from the late 1980s onward and, while production has declined, it remains a reference locality.
• Malacacheta — situated in the Jequitinhonha Valley region of northeastern Minas Gerais, a zone well known for a range of gem chrysoberyl, tourmaline, and aquamarine. Malacacheta material tends toward slightly different colour characteristics compared with Hematita stones, though both localities produce the characteristic Brazilian colour palette.

Smaller occurrences are distributed across other parts of Minas Gerais and, to a lesser extent, in the states of Bahia and Espírito Santo, though none rival Hematita or Malacacheta in historical output.

Colour-Change Characteristics

The defining property of alexandrite — and the criterion by which all specimens are ultimately judged — is the degree, completeness, and attractiveness of its colour change under different light sources. The phenomenon arises because chromium's absorption spectrum in chrysoberyl straddles the boundary between the green and red transmission windows, making the stone's perceived colour highly sensitive to the spectral distribution of the illuminating light.

Russian alexandrite, the historical benchmark, typically shifts from a pure, saturated green in daylight to a rich raspberry or pigeon-blood red in incandescent light — a transformation so complete that early observers famously described it as an emerald by day and a ruby by night. Brazilian material, while governed by the same physics, generally presents a somewhat different and less extreme palette:

• In daylight or fluorescent light: commonly a bluish-green, teal, or greyish-green, rather than the pure vivid green of top Russian stones.
• In incandescent light: typically a purplish-red, brownish-red, or reddish-purple, rather than a clean ruby-red.

The grey or brown modifier present in many Brazilian stones reduces the perceived saturation of both poles of the colour change, which is the primary reason the finest Russian material retains a premium over all but the very best Brazilian examples. However, exceptional Brazilian specimens — those with strong saturation, minimal grey masking, and a shift of 70–100% as assessed by standard gemmological criteria — are genuinely impressive stones and are not to be dismissed as merely second-tier.

Colour zoning is a recognised feature of Brazilian alexandrite. Crystals may display sector or growth-band zoning in which alexandrite alternates with ordinary yellowish or colourless chrysoberyl, a characteristic that can affect the uniformity of the colour change in the finished stone and requires skilled orientation during cutting.

Clarity and Inclusions

Brazilian alexandrite is, as a class, more heavily included than the finest Russian material, though this generalisation requires qualification. Common inclusion types include:

• Needle-like rutile or ilmenite inclusions, sometimes oriented along crystallographic directions.
• Two-phase and three-phase fluid inclusions.
• Fractures and cleavage planes, which can complicate cutting and affect transparency.
• Chrysoberyl twinning, which is common in the species and can produce characteristic V- or heart-shaped twin planes visible under magnification.

Eye-clean Brazilian alexandrite of good colour change is commercially available but commands a significant premium over included material. Stones with strong colour change and acceptable clarity in sizes above two carats are considered genuinely fine and are priced accordingly.

Gemmological Properties

Brazilian alexandrite shares the species properties of chrysoberyl. Key constants include:

• Chemical formula: BeAl₂O₄
• Crystal system: Orthorhombic
• Hardness: 8.5 on the Mohs scale
• Specific gravity: approximately 3.73
• Refractive indices: approximately 1.746–1.763 (biaxial positive)
• Birefringence: approximately 0.009–0.011
• Pleochroism: strong trichroism — green, orange-yellow, and red/purple visible along different crystallographic axes
• Fluorescence: typically weak to inert under long-wave UV; may show weak red under short-wave UV

Origin determination — distinguishing Brazilian from Russian, Sri Lankan, or East African alexandrite — is a service offered by major gemmological laboratories including GIA, Gübelin, and SSEF. Brazilian material can often be identified by its characteristic inclusion assemblage and trace-element chemistry, though origin calls on clean stones remain challenging and are expressed with appropriate qualification in laboratory reports.

Treatment

Alexandrite as a species is not routinely treated, and this applies to Brazilian material. Unlike corundum or emerald, chrysoberyl does not benefit meaningfully from heat treatment, and no filling or coating treatments are standard in the trade. Fracture-filling with resins or oils, while theoretically possible, is not an established practice for alexandrite. Buyers and laboratories therefore expect untreated stones, and any evidence of treatment would be considered highly anomalous and would substantially affect value. Synthetic alexandrite — produced by flux, hydrothermal, and Czochralski pulling methods — is commercially available and must be distinguished from natural material; reputable laboratories can make this determination reliably.

Market Position and Value Factors

The near-exhaustion of Ural Mountain production by the mid-twentieth century, combined with the relatively modest output of Sri Lankan deposits, means that Brazil has supplied the majority of the world's natural alexandrite for several decades. This has given Brazilian material a dominant position in the commercial market, even as Russian stones retain their prestige as the historical and qualitative benchmark.

Value in Brazilian alexandrite is determined principally by:

• Colour-change strength — the percentage and completeness of the shift, assessed under standardised daylight-equivalent and incandescent sources.
• Colour quality at each pole — the purity and saturation of both the daylight and incandescent colours, with grey and brown modifiers reducing value.
• Clarity — eye-clean stones command multiples of the price of visibly included material.
• Carat weight — price per carat escalates sharply above one carat, and again above three carats, reflecting the rarity of large clean crystals.
• Cut quality — proper orientation to maximise colour change, combined with well-executed proportions, is essential.

Fine Brazilian alexandrite above two carats with strong, clean colour change and good clarity has achieved prices of several thousand to tens of thousands of US dollars per carat at major auction houses and specialist dealers. While such stones do not typically reach the per-carat records set by exceptional Russian material, they are recognised as genuinely important gemstones in their own right, and their relative availability in larger sizes gives them a practical advantage in jewellery applications where Russian stones of comparable dimensions simply do not exist on the market.

Further Reading

• GIA Gem Encyclopedia: Alexandrite
• Gems & Gemology: Alexandrite from Brazil (GIA)
• AGTA Gemstone Encyclopedia: Alexandrite