Alexandrite color chart: shades, names and which color is finest
By HeyGema™ · Updated
In short
Alexandrite is the very rare color-change variety of chrysoberyl: bluish green in daylight and purplish red in incandescent light. Cutters and merchants aim for a green or bluish green in daylight that turns red-purple under incandescent light. A round 1 carat alexandrite measures about 6.3 mm.
- 2shades on the chart
- 6.3 mm1 carat, round
- 8.5hardness (Mohs)
Alexandrite colors
Alexandrite is the very rare color-change variety of chrysoberyl: bluish green in daylight and purplish red in incandescent light.
- DaylightA bluish green.
- Incandescent lightA purplish red.
The swatches are illustrations picked to match the color names. Screens and light change how color looks, and a cut stone changes with the light, so judge a stone in person or from a daylight photo.
Which alexandrite color is finest
Cutters and merchants aim for a green or bluish green in daylight that turns red-purple under incandescent light. GIA says fine material is exceptionally rare and valuable.
How gemologists describe color
Gemologists describe the color of a stone with hue, tone and saturation, and look at the three together. For colored stones they also look at how evenly the color is spread.
- Hue
- The color you would name, such as blue, green or red, or a blend such as bluish green.
- Tone
- How light or dark that color looks, from pale to very dark.
- Saturation
- How strong or pure the color looks, from dull (grayish or brownish) to vivid.
- Evenness
- How evenly the color is spread through the stone. Color zoning is uneven color, such as bands or patches you can see.
Colored stones have no single color scale like the D to Z scale for diamonds, so sellers use their own words. Ask for a daylight photo and for the size in mm as well as the carat weight.
What affects alexandrite color
- Cause of color
- Trace chromium replacing aluminum in chrysoberyl. Transparent alexandrite appears to combine chromium and vanadium, and iron also plays a part.
- Treatments
- Lab-grown alexandrite exists, so ask for a lab report.
- Light and angle
- Faceted stones show both pleochroism and color change, depending on cut and orientation.
Alexandrite color and size
Carat is weight, not size. A round 1 carat alexandrite measures about 6.3 mm, against 6.5 mm for a diamond of the same weight. This table gives the face-up size of a well-cut alexandrite.
- 0.5 ct
- Round: 5.0 mm
- Oval: 6.2 x 4.3 mm
- Cushion: 4.4 x 4.4 mm
- 1 ct
- Round: 6.3 mm
- Oval: 7.8 x 5.4 mm
- Cushion: 5.5 x 5.5 mm
- 2 ct
- Round: 8.0 mm
- Oval: 9.9 x 6.8 mm
- Cushion: 6.9 x 6.9 mm
- 3 ct
- Round: 9.1 mm
- Oval: 11.3 x 7.8 mm
- Cushion: 7.9 x 7.9 mm
See the full alexandrite size chart for every shape, or use the carat to mm calculator for any weight.
Alexandrite properties
- Hardness (Mohs)
- Value: 8.5
- Refractive index
- Value: 1.746 to 1.755
- Specific gravity
- Value: 3.73
A chrysoberyl that changes color between daylight and incandescent light. Stones over a carat are scarce.
How to compare alexandrite stones
- Look at each stone in daylight and under indoor light. Color shifts with the light.
- Ask for the size in mm as well as the carat weight. A alexandrite of the same weight can differ in size by shape and cut.
- Ask whether the color is natural or treated, and ask for the answer in writing.
- For a stone that matters, ask for an independent lab report.
Designing with a colored stone? HeyGema lets you choose the stone shade and renders your design with it.