What Is Alexandrite?
Alexandrite is a rare variety of the mineral chrysoberyl (BeAl₂O₄) that displays one of the most dramatic optical phenomena in the mineral kingdom: a distinct color change depending on the light source. Under natural daylight or fluorescent light, fine alexandrite appears green to bluish-green. Under incandescent light or candlelight, the same stone transforms to a vivid red or purplish-red. This chameleon-like behavior is caused by the way chromium — the same element responsible for the color of emeralds and rubies — absorbs light at specific wavelengths.
First discovered in Russia's Ural Mountains in the 1830s, alexandrite was named in honor of Tsar Alexander II. The stone's red-and-green color shift mirrored the imperial Russian military colors, making it an instant sensation among the Russian aristocracy. Today, fine alexandrite is among the most valuable gemstones per carat in the world, often exceeding the price of diamonds, rubies, and emeralds of comparable quality.
How to Identify Alexandrite
Identifying genuine alexandrite requires attention to several key properties:
- Color change: The defining characteristic. A true alexandrite must show a noticeable shift between green (daylight) and red (incandescent light). Stones with only a subtle shift or that change between two shades of the same color are not considered fine alexandrite.
- Hardness: Chrysoberyl registers 8.5 on the Mohs scale — harder than most minerals and second only to corundum (ruby/sapphire) among common gem minerals. A genuine alexandrite will not be scratched by quartz or topaz.
- Crystal system: Orthorhombic. Alexandrite crystals often form as tabular or prismatic shapes, and twinned crystals (cyclic twins forming pseudo-hexagonal shapes) are particularly prized by mineral collectors.
- Luster: Vitreous (glassy) to adamantine.
- Specific gravity: 3.70–3.78, noticeably heavier than most glass imitations.
- Refractive index: 1.746–1.763, measurable with a standard gemological refractometer.
Synthetic alexandrite has been produced since the 1960s using flux-growth and Czochralski (pulled) methods. Synthetic stones show the same color change as natural alexandrite but lack the inclusions and growth features of natural crystals. Under magnification, natural alexandrite often shows needle-like inclusions, fingerprint inclusions, and growth zoning. Lab-grown stones tend to be cleaner and more uniform — a red flag for collectors seeking natural specimens.
Color-change garnets and color-change sapphires are sometimes confused with alexandrite, but these can be distinguished by their different refractive indices and specific gravities.
Famous Localities
The origin of an alexandrite specimen dramatically affects its value and collectibility:
- Ural Mountains, Russia: The original and most legendary source. Russian alexandrite is renowned for its strong, saturated color change — from a rich emerald green to a deep raspberry red. Crystals from this locality are extremely rare on the market today and command extraordinary premiums. Fine Russian alexandrite crystals in matrix are among the most coveted mineral specimens in existence.
- Minas Gerais, Brazil: Brazil became a major source in the 1980s and produces alexandrite with excellent color change, though the green tone is often slightly more yellowish than Russian material. Brazilian alexandrite is more available on the market and represents the benchmark for most modern collector material.
- Sri Lanka (Ceylon): Sri Lankan alexandrite tends toward a more muted color change, often shifting between olive green and brownish-red. However, large crystals are found here, and some exceptional stones rival Russian material.
- Tunduru, Tanzania: Tanzanian alexandrite can show vivid color change and is increasingly appreciated by collectors. Some material rivals Brazilian quality.
- Andhra Pradesh, India: India produces alexandrite in significant quantities, though quality is variable. Some fine crystals have been recovered.
Rarity and Value
Fine natural alexandrite is genuinely one of the rarest minerals on Earth. The combination of factors required for its formation — the right chemistry, the right geological conditions, and the presence of chromium in an environment where beryllium and aluminum are also available — is extraordinarily uncommon. Chromium and beryllium rarely occur together in nature, which is why alexandrite deposits are so scarce.
For faceted gems, the value hierarchy is roughly: strong color change > color saturation > clarity > size. A fine 1-carat Russian alexandrite with strong color change can sell for $15,000–$70,000 per carat. Brazilian material of similar quality typically ranges from $5,000–$15,000 per carat. For mineral collectors, crystal specimens in matrix — especially twinned crystals — are prized above faceted stones for their scientific and aesthetic value.
Caring for Your Alexandrite Specimens
Alexandrite's hardness of 8.5 makes it relatively durable, but proper care ensures your specimens remain pristine:
- Storage: Store alexandrite specimens separately from harder minerals (only diamond and moissanite are harder). While alexandrite won't be scratched by most minerals, it can scratch softer specimens in your collection. Use individual compartments, padded trays, or specimen boxes.
- Cleaning: Clean with warm water and a soft brush. Mild dish soap is safe. Avoid ultrasonic cleaners if the specimen has fractures or inclusions that could be stressed by vibration. Avoid steam cleaning.
- Light exposure: Alexandrite is stable under normal light conditions and does not fade. However, prolonged direct sunlight is best avoided for any mineral specimen as a general precaution.
- Handling: Always handle specimens with clean hands or cotton gloves to avoid transferring oils to the surface. The natural oils from skin can dull the luster of any mineral over time.
Adding Alexandrite to Your Collection
For serious collectors, alexandrite represents one of the ultimate acquisitions — a mineral that is simultaneously a world-class gemstone, a fascinating scientific specimen, and a piece of geological history. Whether you're drawn to a twinned crystal from the Ural Mountains, a faceted gem that shifts dramatically under different lights, or a matrix specimen showing alexandrite's natural crystal habit, this mineral rewards careful study and appreciation.
When purchasing alexandrite, always request documentation of origin when possible, and for significant purchases, consider obtaining a certificate from a reputable gemological laboratory (GIA, AGL, or Gübelin) that confirms natural origin and locality. The difference between a natural Russian alexandrite and a synthetic stone can represent a tenfold difference in value.