How to Identify Real Alexandrite Gemstones

Alexandrite is one of the most misrepresented gemstones in the market. Its rarity makes it commercially valuable, and that value creates a persistent incentive to pass off simulants, synthetic material, and colour-change stones of other species as the real thing. For a buyer approaching alexandrite gemstones for the first time, whether for a ring, a pendant, a loose stone, or an investment, knowing how to distinguish genuine alexandrite from what merely resembles it is not an academic exercise. It is the difference between acquiring something rare and acquiring something common at a rare stone's price. 

This guide explains what natural alexandrite gemstones actually are, how genuine colour change works and what it looks like in practice, how alexandrite compares to its common substitutes, and what tools and expertise are needed to make a confident identification. It also covers the different cut forms in which alexandrite is commonly found, from the oval and emerald cut to the less familiar pear and shield cuts, and what those shapes tell you about how a stone was fashioned. 

What Defines a Real Alexandrite Gemstone 

Alexandrite is a variety of the mineral chrysoberyl, not corundum, not quartz, not garnet. It is distinguished from other chrysoberyl by the presence of chromium as a trace element, which is responsible for both its green colour in daylight and its red-to-purplish colour under incandescent light. This colour change is not a surface effect and not a trick of the stone's shape or cut. It is a physical property of the material itself, determined by how chromium absorbs specific wavelengths of light. 

A real alexandrite gemstone must meet two criteria simultaneously: it must be chrysoberyl in mineralogical composition, and it must display a genuine shift in colour between daylight and incandescent light sources. A stone that satisfies only one of these conditions - chrysoberyl without colour change, or colour change without being chrysoberyl is not alexandrite. This seems straightforward, but the market offers multiple stones and materials that meet one criterion while failing the other, and the distinction requires either laboratory equipment or a trained gemmologist to confirm. 

The Colour Change: What Real Alexandrite Looks Like 

The colour change in a natural alexandrite gemstone is the stone's most defining and most misunderstood characteristic. Because fine specimens with vivid, dramatic shifts are frequently described in print, many buyers arrive with unrealistic expectations about what the colour change should look like and either dismiss genuine stones that do not match the ideal or accept simulants whose colour shift superficially resembles the textbook description. 

The Realistic Colour Range 

The celebrated "emerald by day, ruby by night" description applies to the finest Russian alexandrite, a category of stone so rare that even experienced gemmologists may never handle one. In the broader market for natural alexandrite gemstones, the colour change is real but more restrained. Daylight colours typically range from various greens: teal, grey-green, olive, and cooler blue-green tones are all common. Under incandescent light, the same stone shifts to purplish-pink, mauve, warm raspberry, or brownish-red. 

A stone that shifts from a grey-green to a clear purplish-pink under a warm lamp is a genuine colour-changing alexandrite gemstone. The shift does not need to be dramatic to be real. What matters is that it is consistent, repeatable, and visible under the appropriate light sources, not dependent on a particular angle or an unusual light. 

How to Test Colour Change at Home 

The most accessible test for colour change requires only two light sources: natural daylight or a cool-white LED (which approximates daylight), and a standard incandescent bulb or a warm candle flame. Take the stone to a window in good natural light and observe its colour. Then take it to a room lit by a single incandescent bulb, no mixed lighting, and observe again. A genuine colour change will be visible to the naked eye as a distinct shift in hue. 

Mixed lighting environments, such as offices with fluorescent and natural light combined, or rooms with multiple light sources of different temperatures, make the colour change harder to observe and can cause a genuine alexandrite to appear as though it is not shifting. Always assess colour change in controlled, single-source lighting. 

What Colour Change in Alexandrite Does Not Look Like 

Colour change in alexandrite is a shift in hue from a greenish family to a pinkish or reddish family. It is not a change in brightness or saturation alone. A stone that simply appears darker or lighter depending on the angle is not displaying colour change. A stone that shifts from one shade of purple to a slightly different shade of purple is not displaying alexandrite's characteristic change. The hue shift must cross from the green or blue-green part of the spectrum to the red or pink part of the spectrum. 

Common Alexandrite Simulants: What to Watch For 

Several materials are sold as alexandrite, sometimes through ignorance and sometimes through deliberate misrepresentation. Knowing the most common substitutes is the first line of defence for any buyer. 

Synthetic Corundum (Colour-Change Sapphire) 

Synthetic colour-change corundum has been sold as alexandrite for over a century. It produces a genuine colour change, typically from greyish-blue or purple in daylight to reddish-purple or brownish-red under incandescent light - but it is not alexandrite. The colour shift in synthetic corundum tends to run from purple to purple-red rather than from green to red or pink, which is one visible clue. More definitively, corundum has a refractive index and specific gravity distinct from chrysoberyl, both measurable with standard gemmological instruments. 

Colour-Change Garnet 

Colour-change garnet is a naturally occurring gemstone, not a synthetic, that can produce a striking shift from green or blue-green in daylight to red or purplish-red under incandescent light. This shift can closely resemble alexandrite's colour change to an untrained eye, and fine colour-change garnets are genuinely beautiful and valuable in their own right. The distinction matters because garnet rates 6.5 to 7.5 on the Mohs scale (lower than alexandrite's 8.5), has a different refractive index, and is priced differently. A gemmologist can distinguish the two readily; a buyer cannot rely on visual inspection alone. 

Synthetic Alexandrite 

Laboratory-grown alexandrite is chemically and optically identical to natural alexandrite. It is genuine alexandrite in every scientific sense it displays real colour change, real hardness of 8.5, and real chrysoberyl composition. The only difference is origin: it was grown in a laboratory rather than formed in the earth. Synthetic alexandrite should always be disclosed as such by the seller. It is not a fraud if disclosed; it is only a problem when sold as a natural material without disclosure. For buyers seeking natural alexandrite gemstone value and rarity, the distinction is significant and must be established by laboratory testing. 

Glass and Simulants 

Glass can be manufactured to display a rudimentary colour shift, though it rarely produces a convincing change across the green-to-red spectrum. Glass is immediately distinguishable by its low hardness (it can be scratched with a steel tool), its lack of double refraction under a loupe, and its characteristic inclusions bubbles, swirl marks, and a glassy lustre quite different from the vitreous but clean transparency of chrysoberyl. Any stone offered at a very low price, such as alexandrite, warrants particular scrutiny. 

Gemmological Tests for Identifying Natural Alexandrite Gemstones 

Visual inspection, however informed, is not sufficient to confirm that a stone is a natural alexandrite gemstone. The following tests, performed by a qualified gemmologist with standard equipment, provide the evidence needed. 

Refractive Index 

Chrysoberyl has a refractive index of approximately 1.746 to 1.755. This distinguishes it clearly from corundum (1.762 to 1.770), garnet (single refractive, varying by species), and glass. A refractometer reading takes seconds and is one of the most reliable first-line tests. Combined with observation of double refraction under a loupe, it narrows the identification significantly. 

Specific Gravity 

Chrysoberyl has a specific gravity of approximately 3.73. This is measurable with a hydrostatic balance and distinguishes alexandrite from colour-change garnets (which vary by species but tend to fall in the 3.6 to 4.0 range) and corundum (4.0). While specific gravity alone does not confirm identification, it contributes to the body of evidence. 

Spectroscopic Analysis 

Under a spectroscope, natural alexandrite shows a characteristic chromium absorption spectrum. This is one of the most definitive tests for the presence of chromium as the colouring agent, which is what separates alexandrite from other chrysoberyl varieties. A Chelsea colour filter, while not definitive on its own, causes chromium-coloured stones to fluoresce red, which is consistent with alexandrite. 

Inclusions Under Magnification 

Natural alexandrite gemstones commonly contain characteristic inclusions: fine needles, two-phase inclusions (liquid with a gas bubble), fingerprint inclusions, and crystal inclusions. The specific nature and arrangement of inclusions can provide strong supporting evidence for natural origin and for the specific geographic source. Laboratory-grown alexandrite typically shows different growth features, curved striae, gas bubbles in flux-grown material, or chevron growth patterns - that a trained gemmologist can recognise under magnification. 

Laboratory Certification 

For any significant purchase of a natural alexandrite gemstone, laboratory certification from a recognised gemmological laboratory provides the most authoritative confirmation of identity, natural origin, treatment status, and, where determinable, geographic source. At Gems and Gold, our alexandrite gemstones are assessed by our in-house gemmologist, and laboratory documentation is provided where appropriate. We are transparent about whether a stone is natural or laboratory grown, and we welcome questions about any stone in our collection before a purchase is made. 

Alexandrite Gemstone Cuts: What the Shape Tells You 

The cut of an alexandrite loose gemstone is not merely an aesthetic decision. It is a statement about how the cutter valued the rough, and it can tell you something about the origin and quality of the material. 

Oval Cut Alexandrite 

The oval is the most common cut for fine natural alexandrite loose gemstones. It maximises the face-up area of the rough while retaining weight, and its brilliant-style faceting produces both good colour saturation and attractive sparkle. An oval-cut alexandrite loose gemstone is also among the most versatile shapes for setting in jewellery - it suits rings, pendants, and earrings equally well. Most Sri Lankan alexandrite in the fine market is cut as ovals. 

Emerald Cut Alexandrite 

The emerald cut, a rectangular step cut, displays alexandrite's colour in broad, even planes rather than in the fractured brilliance of a mixed or round cut. This makes it a demanding cut for alexandrite: the colour must be even and the clarity sufficient to sustain the transparency that step cutting requires. An emerald-cut alexandrite loose gemstone tends to show the colour change in a more measured, architectural way, with less sparkle and more depth. It is a cut that suits buyers who value the stone's character over its brilliance. 

Pear Cut Alexandrite 

The pear cut combines a rounded base with a pointed apex, producing a shape that elongates elegantly in a pendant or a ring. A pear-cut alexandrite gemstone displays colour shift attractively across its length, though the pointed tip requires careful setting to protect against chipping. Pear cuts are less common in alexandrite than ovals, which makes them a distinctive choice for alexandrite gemstone jewellery that stands apart from the standard. 

Shield Cut Alexandrite 

The shield cut, a modified geometric shape with straight or slightly curved sides forming a broad, shield-like outline, is among the less commonly seen cuts in alexandrite. It is typically used for material with unusual proportions in the rough, or by cutters seeking to maximise weight from irregular crystals. A shield-cut alexandrite gemstone has a distinctive presence and is often a one-of-a-kind piece. The flat, broad faceting of many shield cuts suits alexandrite's colour display well, presenting the shift across a wide face-up area. 

Alexandrite Gemstone Value: What Drives the Price 

Understanding alexandrite gemstone value requires understanding which characteristics the market rewards and why. 

• Colour change strength: the primary value driver. A stone with a strong, clearly visible shift from one distinct hue to another commands a significant premium over a stone with a weak or partial change. The shift does not need to be green-to-red to be valuable - a clear green-to-purple change is well regarded - but a change that is barely perceptible is reflected in the price. 
• Colour quality in each light: a stone with a vivid, lively colour in both its daylight and incandescent presentations is more valuable than one with a strong shift between two dull or muted tones. Saturation and tone in both lighting conditions contribute to value independently of the shift itself. 
• Natural versus laboratory-grown: natural alexandrite gemstone value is substantially higher than that of laboratory-grown material of equivalent apparent quality. The premium reflects genuine geological rarity. Fine natural alexandrite above one carat with strong colour change is among the most expensive coloured gemstones per carat. 
• Origin: Sri Lankan alexandrite is the most widely available natural material. Brazilian alexandrite tends to produce a slightly different colour profile. Fine material from any origin commands a premium; stones with documented provenance are valued above undocumented equivalents. 
• Carat weight: fine natural alexandrite in sizes above one carat is disproportionately rare. Price per carat escalates sharply with size - a two-carat stone with fine colour change is not twice the price of a one-carat equivalent; it is considerably more. 
• Cut quality: a well-proportioned cut that maximises colour display and minimises windowing (the transparent, colourless area visible in poorly cut stones) adds measurable value. Alexandrite rough is too valuable to cut carelessly, and well-cut stones command a premium over poorly proportioned equivalents of identical weight. 

Benefits of Alexandrite Gemstone 

From a purely practical perspective, the most durable benefit of owning a natural alexandrite gemstone is the rarity itself. Fine natural alexandrite is not being produced in greater quantities as time passes the geological deposits are finite and increasingly depleted. A well-chosen stone, properly documented and well set, is a genuinely rare object whose scarcity will only increase. 

Alexandrite Gemstone Ring: Choosing a Setting for a Loose Stone 

For those purchasing alexandrite loose gemstones with the intention of having them set, the choice of setting is as important as the choice of stone. The setting must protect the stone without obscuring the colour change that makes it remarkable. 

• Metal choice: yellow gold is the warmest complement to alexandrite's incandescent colour. Rose gold works similarly. Platinum and white gold provide maximum contrast for the daylight green. The choice depends on which colour presentation the wearer most values, and which metal suits their broader jewellery wardrobe. 
• Setting style: a bezel or half-bezel provides the most physical protection, which matters given that alexandrite, while hard at 8.5, can chip at sharp facet edges under impact. A claw setting maximises light entry and colour display but requires regular maintenance. 
• Profile and proportion: the setting should be proportioned to the specific stone rather than adapted from a standard template. The colour change of a natural alexandrite gemstone ring is best displayed in a setting that allows the stone to be viewed from above in both daylight and lamplight. The face-up view is primary. 
• Commission versus ready-made: a significant natural alexandrite loose gemstone is worth commissioning a bespoke setting for. A ready-made setting calibrated for a standard size may require adaptation, and the setting of a rare stone is not the place to compromise on craftsmanship. 

Our Alexandrite Gemstone Collection 

At Gems and Gold, we carry natural alexandrite gemstones sourced from Sri Lanka, assessed individually by our in-house gemmologist for colour change quality, clarity, and cut. We offer alexandrite loose gemstones across a range of cuts - oval, emerald cut, pear, and others as they become available, as well as finished alexandrite gemstone rings and jewellery. Each stone is accompanied by documentation stating its natural origin and treatment status. 

If you are purchasing alexandrite for the first time, or looking for a specific cut or quality level, we welcome the opportunity to guide you through what is available and help you understand what you are looking at. 

Explore our natural alexandrite gemstone collection at gemsandgold.com.au