Ruby color chart: shades, names and which color is finest
By HeyGema™ · Updated
In short
Ruby is red corundum. GIA describes the ideal as a vivid red with a slight purple cast and strong saturation, neither too dark nor too light. A round 1 carat ruby measures about 6.2 mm.
- 4shades on the chart
- 6.2 mm1 carat, round
- 9hardness (Mohs)
Ruby colors
Ruby is red corundum. Chromium gives it its red, and the hue runs from orangy red to purplish red.
- Vivid red, slightly purplishThe color most often called the finest.
- Orangy redA red that leans toward orange.
- Purplish redA red that leans toward purple.
- Lighter pinkish redA lighter tone. Where it stops being ruby and becomes pink sapphire has no numeric line.
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 ruby color is finest
GIA describes the ideal as a vivid red with a slight purple cast and strong saturation, neither too dark nor too light. The phrase pigeon's blood names the top of the range, but it is loosely defined and GIA advises avoiding it.
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 ruby color
- Cause of color
- Chromium. More chromium gives a stronger red.
- Treatments
- Most ruby is heated. Some has color diffused into the surface or fractures filled with lead glass. Unheated stones with an independent lab report earn a premium, and diffused or glass-filled stones are valued lower than heated ones. Glass filling can be damaged by heat and by acids such as lemon juice.
- Light and angle
- The glow of the finest stones is fluorescence, not a color change.
- Wear and care
- Ruby is very hard and tough, and it has no cleavage.
Ruby color and size
GIA says large blue sapphires are easier to find than large rubies. Carat is weight, not size. A round 1 carat ruby measures about 6.2 mm, against 6.5 mm for a diamond of the same weight. This table gives the face-up size of a well-cut ruby.
- 0.5 ct
- Round: 4.9 mm
- Oval: 6.1 x 4.2 mm
- Cushion: 4.3 x 4.3 mm
- 1 ct
- Round: 6.2 mm
- Oval: 7.7 x 5.3 mm
- Cushion: 5.4 x 5.4 mm
- 2 ct
- Round: 7.8 mm
- Oval: 9.7 x 6.6 mm
- Cushion: 6.8 x 6.8 mm
- 3 ct
- Round: 8.9 mm
- Oval: 11.1 x 7.6 mm
- Cushion: 7.7 x 7.7 mm
- 5 ct
- Round: 10.6 mm
- Oval: 13.1 x 9.0 mm
- Cushion: 9.2 x 9.2 mm
See the full ruby size chart for every shape, or use the carat to mm calculator for any weight.
Ruby properties
- Hardness (Mohs)
- Value: 9
- Refractive index
- Value: 1.762 to 1.770
- Specific gravity
- Value: 3.95 to 4.03
Red corundum, the same mineral as sapphire. Denser than diamond, so it faces up smaller for its weight.
How to compare ruby 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 ruby 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.