Gemstone Color Measurements and Specifications


One of the great challenges of gemology is the development of an accurate, simple, consistent, and reproducible technique for gemstone color measurements and specifications. Until the mid-80s little progress was made, despite the appearance and widespread promotion of various color-chart systems. None of these systems are satisfactory for gemology, chiefly because: 1. They don’t adequately cover the total range of gem colors, 2. They don’t offer enough detail in the ranges they do cover, and 3. The color-chart materials (printed colors and transparencies) are of insufficient quality to prevent variations in production runs. The ideal solution is a gemstone colorimeter. However, such an instrument must deal with the unique optical properties of gems, such as brilliancy and pleochroism, which make gemstones extremely difficult specimens for instrumental measurement.

Figure 3. Munsell color wheel. (From Precise Color Communication: Color Control from Feeling to Instrumentation, p.19; courtesy of Minolta Camera Company, Ltd. Japan.)
Munsell color wheel. (From Precise Color Communication: Color Control from Feeling to Instrumentation, p.19; courtesy of Minolta Camera Company, Ltd. Japan.)

Three-Dimensional Color Space

The science of colorimetry is well established in almost all areas of endeavor where color is important, such as paint, plastics, textiles, and other industrial and consumer materials. Objective instrumentation is now routinely used in these fields. However, before such instruments were available people had to rely on visual systems such as color charts for specifying color. These charts are sections of what we may refer to as three-dimensional color space. These dimensions are termed hue, lightness, and saturation.

Hue

Hue is the attribute we are describing when we speak of red, yellow, green, blue, purple, and other hues intermediate to adjacent pairs in this series. These hues can be readily visualized in terms of a color wheel.

Lightness

Also called value, lightness is a scale with white and black as endpoints and shades of gray in between. Note, however, that all chromatic colors can also be scaled to lightness as a function of their total reflectance. Lightness can be visualized in terms of a vertical axis with white at the top and black at the bottom.

Figure 1. Three-dimensional color system. (From Precise Color Communication: Color Control from Feeling to Instrumentation, p.8; courtesy of Minolta Camera Company, Ltd. Japan.)
Three-dimensional color system. (From Precise Color Communication: Color Control from Feeling to Instrumentation, p.8; courtesy of Minolta Camera Company, Ltd. Japan.)

Saturation

Also called chroma, saturation is a measure of the amount of hue in a color, its vividness, or how much it differs from a gray of the same lightness. Chroma can be seen in vertical sections of three-dimensional color space. A section along a specific radial direction of the color circle is designated as a specific hue. Lighter shades of this hue are near the top of the section, darker shades at the bottom. The chroma (vividness) of the hue increases moving outward from the central axis. The range of chroma varies with both hue and lightness, making the color solid an irregular shape, rather than a simple ovoid or sphere.

Figure 2. Color solid. (From Precise Color Communication: Color Control from Feeling to Instrumentation, p.9; courtesy of Minolta Camera Company, Ltd. Japan.)
Color solid. (From Precise Color Communication: Color Control from Feeling to Instrumentation, p.9; courtesy of Minolta Camera Company, Ltd. Japan.)

Color-Order Systems

Subdividing the color solid into smaller units and giving each a name or set of numerical coordinates can achieve color specification. This results in a classification known as a color-order system. The color solid can be subdivided in many ways. Not surprisingly, there are also many color-order systems.

Some of the color-order systems created during the early decades of the 20th century were represented by charts made of paint colors coated on paper. Architects and designers used Wilhelm Ostwald’s system for color selection and specification. Biologists used Robert Ridgway’s system for classifying thousands of flora and fauna specimens. (Some of these older systems, like Ostwald’s and Ridgway’s, are still used today). Thus the need for accurate color measurements and specifications was firmly established before instruments and related color-order systems were available.

The A.H. Munsell System

Perhaps the most popular and widespread of the chart-type color-order systems is the one devised by A.H. Munsell and extensively revised by the Optical Society of America (OSA) in 1943. The Munsell hue scale is based on five hues equally spaced around the hue circle (red, yellow, green, blue, purple) and intermediate hues (yellow-red, green-yellow, blue-green, purple-blue, red-purple). The major hues are abbreviated R,Y,G, B, and P, and the intermediate hues YR, GY, BG, PB, and RP.

Further subdivision results in forty hue charts in the Munsell Book of Color. Colors appear on these charts at value (lightness) intervals of one unit from 2 to 9. Chroma (saturation) is represented in whole units ranging from 2 (near-gray) in two-step intervals up to as high as 14 and 16 for the most vivid colors.  The notation system is decimal, allowing colors to be specified accurately. Munsell color books are available in both matte and high gloss finish, with the latter having about fifteen hundred colors.

Figure 4. Munsell value and chroma for hue 5G. (From Precise Color Communication: Color Control from Feeling to Instrumentation, p.17; courtesy of Minolta Camera Company, Ltd. Japan.)
Munsell value and chroma for hue 5G. (From Precise Color Communication: Color Control from Feeling to Instrumentation, p.17; courtesy of Minolta Camera Company, Ltd. Japan.)

All these color-order systems (including the more recent German standard DIN 6164 and the Swedish Standard Natural Colour System) have certain similarities. Color sampling is along lines of constant hue (or a similar metric). Thus, corresponding colors on adjacent hue charts become visually farther apart as they become progressively more saturated (that is, move further away, radially, from the center of the color circle). Thus, the most vivid colors are more distant from each other than less vivid ones, often by a factor of five or more.

These color charts are inadequate for gemstone color measurements because they don’t have sufficient colors in the vivid color regions and they don’t extend far enough for gem analysis. The color ranges of vivid, transparent gemstones simply can’t be captured with opaque colors on paper. In addition, opaque paint colors don’t look like transparent gemstones, even when the colors are, in fact, the same.

The CIE System

A major step forward came in 1931 when the international adoption of the Commission Internationale de l’Eclairage (CIE) system resulted in greater interest in color measurements and specifications, especially by colorimetry. The CIE system included standard illuminants (incandescent, sunlight, north daylight), a standard observer, and standard response functions of the human visual system. The CIE continues as the principal international organization in the field of color research and standardization. Since 1931, it has made important improvements and additions to the original concept.

The color industry was built around research and development of spectrophotometers and colorimeters capable of making measurements and reporting data in CIE terms. However, this created a problem with existing color-order systems. Such systems are necessarily spaced visually for their appearance under a specific light source. Visual spacings and overall appearance will be altered accordingly if other sources are used. If CIE data are published for such colors, the numbers are valid only for the light source for which the measurement data were computed.

CIE color space is visually non-uniform. A more uniform color space makes specification of tolerances and small color differences more meaningful and is therefore more useful to science and industry. Extensive research has been done to produce mathematical transformations of CIE data into a more visually uniform color space.

The Hunter System

In 1942 Richard S. Hunter designed a filter colorimeter for the measurement of opaque surface colors and, to accompany it, the Hunter color-order system. This is a transformation of CIE data using simple equations that were incorporated into the computational elements of the instrument. Hunter space was of the “opposite-hue” or “opponent-hue” type as shown below.

Figure 5A. Lab color space as conceived by Richard S.Hunter
Lab color space as conceived by Richard S.Hunter

When Hunter a attribute is positive, the color has redness; when negative, greenness. Similarly, when b is positive the color has yellowness; when negative, blueness. The third Hunter attribute was L for lightness. Equal steps along the three scales (L,a,b) were intended to represent equal visual steps in the several color directions, permitting color differences to be simply computed by the formula:

ΔΕ= √(ΔL²+ Δa²+ Δb²)

Where delta (Δ)Ε denotes color difference.

It’s common practice today for color-measuring instruments to include Hunter color notations as a readout option for measurement results. Although material color samples were never produced to illustrate Hunter color space, the nearly uniform visual spacing became very useful for describing color specifications and tolerances in industry and contributed importantly to the sale and use of these instruments.

CIELAB Space

The CIE and others continued working to provide a color space with improved visual spacing. In 1976, CIELAB space was recommended. Similar to Hunter space, CIELAB space is a mathematical transform of CIE data and is plotted on rectangular coordinates. CIELAB color attributes are designated L* (L-star), a* (a-star), and b* (b-star) to distinguish them from Hunter and have the same nominal meanings. As with Hunter, CIELAB is a standard readout on current instruments.1

Figure 6. L*a*b* and Munsell notations (hue, value). For extremely small or large a*b* values, multiply or divide them by an appropriate amount before plotting and reading the hue values.(From Precise Color Communication: Color Control from Feeling to Instrumentation, p. 19; courtesy of Minolta Camera Company, Ltd. Japan.)
L*a*b* and Munsell notations (hue, value). For extremely small or large a*b* values, multiply or divide them by an appropriate amount before plotting and reading the hue values.(From Precise Color Communication: Color Control from Feeling to Instrumentation, p. 19; courtesy of Minolta Camera Company, Ltd. Japan.)

The OSA-UCS System

The Optical Society of America-Uniform Color Spacing system (OSA-UCS), an opponent-hue system developed by the Optical Society of America, is not only an improvement over Munsell spacing but is also a direct CIE transformation. The OSA-UCS colors (at this writing 558 colors, available as 2 x 2 inch samples) are in scales with intervals of two units in chromaticity and one in lightness. A prototype OSA color collection produced in Denmark shows chromaticity scale intervals of only one unit, with lightness increments of 0.5 and over two thousand colors. The OSA-UCS colors are the best example of uniform color spacing produced to date and will probably appear soon as a readout option on instruments.

Gemstone Color Measurements

Some gemologists have tried unsuccessfully to use existing color instrumentation to characterize gemstones. Instrument makers haven’t perceived gemology to warrant the costly research and development necessary to devise instruments specifically applicable to gemstones. The existing color charts and simplistic optical devices currently in use by gemologists are severely limited in accuracy and usefulness.

The recent marketing by Minolta Camera Co. of a lower cost portable colorimeter motivated several researchers to modify this instrument for gemstone colorimetry. One of the first was Dr. Richard Pettijohn. He attempted to adapt the Minolta sensor unit for specific use with gemstones by reducing the beam size and adding a glass plate to hold the sensor and a small mirror to reflect light passing through the stone to the sensor. However, this arrangement was too inaccurate and non-repeatable to be a viable solution. Moreover, the mirror arrangement dictates the “standard” illuminant for measurement to be the xenon flashlamp built into the unit rather than an independently measured white standard.

J. Rennilson and W.N. Hale devised an improved version of this instrument, also using the Minolta colorimeter. This replaces the glass and mirror with a small white-lined integrating sphere. A 2-mm light beam from below illuminates a gemstone mounted on a clear plate centered within the sphere. Light reflected from the gem is mixed with that transmitted through it and picked up by a detector outlet in the sphere wall. This colorimeter, with patented illuminating and collection geometry, is sufficiently accurate and repeatable for gemstone work. The data readout is in CIE data (Y,x,y) and CIELAB (L*,a*,b*), for CIE standard illuminant D65 or C (both representative of standard daylight in slightly different form). This kind of instrumentation will likely totally revolutionize the gemstone field, bringing order and objective reality to a chaotic system of vague and often obsolete terminology for gemstone color measurements and specifications.

The Rennilson-Hale instrument was not yet available when the Table of Gemstone Color Measurements at the end of this article was prepared. The Pettijohn instrument was therefore used. The illuminating and viewing geometry produce results that are neither as accurate nor consistent as the integrating sphere/fiber optic system of Rennilson and Hale. Also, the conversion of CIELAB data to Munsell notation was done by the Minolta DP-100 micro-computer.2

Table 3 Munsell (chroma C) and L*a*b* (chroma c*) notations Source: (From Precise Color Communication: Color Control from Feeling to Instrumentation, p. 19; courtesy of Minolta Camera Company, Ltd. Japan.) Note: In columns with two digits, left figures are for hues 1-5 and right for hues 6-10
Munsell (chroma C) and L*a*b* (chroma c*) notations
Source: (From Precise Color Communication: Color Control from Feeling to Instrumentation, p. 19; courtesy of Minolta Camera Company, Ltd. Japan.) Note: In columns with two digits, left figures are for hues 1-5 and right for hues 6-10

Errors in conversion may arise due to the limited data storage capacity of this device.3 Further errors are inevitable when trying to illustrate gemstones by photography and printed reproduction on paper.4 Therefore, the tabulated numerical color data must not be considered accurate enough to establish benchmark points for specific gemstone species. However, this degree of error is small compared to the actual variation in color exhibited by most species. The real purpose of this article and these measurements is to establish, for the first time in the gemological literature, the nomenclature, direction, and methodology for scientific, accurate, reproducible, and objective gemstone color measurements and specifications. The numbers themselves are considered less important in this context than an understanding of how they were obtained and the implications of this new technology for gemology and the gemstone marketplace.

NOTES

Dr. Joel Arem is deeply grateful to W. N. Hale, Jr., private color consultant and 22-year veteran of Munsell Color Co., Inc. (as both president and technical director), who provided substantial portions of this text. (Hale Color Consultants, Inc., 1505 Phoenix Road, Phoenix, MD. 21131)

  1. In CIELAB terminology, chroma is calculated from a* and b* as follows: Chroma = C* =√(a*²+b*²)
  2. Invaluable assistance in converting measured L*a*b* values to Munsell numbers, along with many valuable suggestions, was provided by Richard E. McCarty of Silver Spring, Maryland.
  3. Color data on gemstones reported herein are in the form of CIELAB readout and corresponding Munsell notation. The conversion to Munsell numbers are direct CIELAB conversions. No attempt has been made to simplify the resulting Munsell values in accordance with the limited range of actual Munsell color samples. This approximation is left to the reader.
  4. Many of the gemstones photographed in Arem’s Color Encyclopedia of Gemstones were measured with the Pettijohn-Minolta colorimeter. These gems are cross-referenced by notation in the section of color plates at the back of Arem’s Color Encyclopedia, and the tabulated color information herein refers to specific gemstone colors, shapes, and weights, facilitating easy correlation with photographs.

TABLE OF GEMSTONE COLOR MEASUREMENTS

Gemstone Color Weight Shape Location L*a*b* Munsell
Actinolite dark green 0.63 Tanzania 56 -7.7 9.1 7.6GY 5.5/1.7
Adamite light green 0.86 Mapimi, Mexico 82 -0.6 26.0 3.2Y 8.2/3.8
Andalusite brown-green 9.55 emerald cut Brazil 58 -3.5 49.0 5.7Y 5.7/6.9
light brown-green 4.72 antique Brazil 60 1.0 14.1 1.9Y 5.9/2.1
medium brown-green 2.92 round Brazil 38 1.6 20.0 2.8Y 3.7/2.9
Anglesite yellow 6.99 fancy Morocco 75 2.7 50.0 2.1Y 7.4/7.4
Amblygonite light yellow 10.10 round Brazil 80 5.3 11.4 5.3YR 7.9/2/1
light yellow 24.6 antique Brazil 95 -3.5 20.0 6.0Y 9.4/2.8
Apatite violet 0.59 emerald cut Maine 71 10.3 15.0 3.1P 7.0/4.0
violet 1.02 hexagon Maine 75 6.0 -7.2 4.9P 7.5/2.0
yellow-green 8.05 rhomboid Canada 68 -11.3 32.1 1.9GY 6.7/4.5
yellow 8.70 antique Mexico 83 -6.2 36.0 6.7Y 8.2/5.0
dark blue 0.55 round Brazil 34 -10.2 -40.6 9.7B 3.3/10.4
medium blue 0.86 oval Brazil 52 -22.8 -25.9 4.6B 5.1/7.8
gray-blue 0.77 round Burma 50 -7.5 1.0 4.6BG 4.9/1.5
light green 12.40 round ? 42 -6.2 9.8 5.3GY 4.1/1.6
dark green 2.87 round Brazil 31 -16.4 12.3 0.1G 3.0/3.2
medium green 1.09 round Brazil 61 -11.2 11.9 8.5GY 6.0/2.4
light blue 1.07 emerald cut Madagascar 76 -20.2 -4.1 7.0BG 7.5/4.2
Axinite medium brown 1.45 round Baja, Mexico 42 10.7 9.3 10.0R 4.1/2.6
dark brown 8.0 pear Baja, Mexico 21 14.2 20.6 4.8YR 2.0/4.2
Benitoite pale blue 0.66 round California 85 5.6 -7.6 4.4P 8.4/2.0
medium blue 1.07 round California 68 4.5 27.0 6.6PB 6.7/6.3
dark blue 1.19 round California 46 8.4 -29.1 7.1PB 4.5/7.0
Beryl
Aquamarine dark blue 2.40 oval Coronel Murta Mine, Brazil 61 -2.7 -17.5 2.8PB 6.0/4.3
dark blue 66.53 antique Brazil 38 -6.0 -8.0 5.8B 3.7/2.3
dark blue 45.40 emerald cut Brazil 54 4.0 -11.0 0.5PB 5.3/2.8
medium light blue 18.08 emerald cut Brazil 80 -6.9 -9.0 8.2B 7.9/2.7
medium blue 21.80 pear Africa 65 -3.5 -18.0 2.6PB 6.4/4.4
Emerald pale green 0.32 round Colombia 85 -12.0 2.6 8.9G 8.4/2.2
light yellow-green emerald cut Colombia 55 -55.0 15.0 6.0G 5.4/10.1
medium green 0.88 emerald cut Chivor Mine, Colombia 70 -41.7 2.5 2.0BG 6.9/8.0
dark blue-green 1.35 emerald cut Muzo Mine, Colombia 46 -73.2 9.1 8.3G 4.5/13.6
dark green emerald cut Zambia 40 -60.0 15.0 6.0G 3.9/11.0
light blue-green 1.96 emerald cut Nigeria 68 -23.5 0.5 2.7BG 6.7/4.6
Green beryl light green 11.25 round Brazil 65 -3.5 6.5 4.3GY 6.4/1.0
light yellow-green 18.42 triangle Brazil 75 -5.1 13.2 2.0GY 7.4/1.9
greenish-yellow 19.09 antique Brazil 70 -9.3 21.1 3.2GY 6.9/3.2
blue-green 4.54 emerald cut Brazil 68 -5.2 3.1 2.0G 6.7/1.0
Golden beryl dark yellow 20.00 emerald cut Brazil 63 -8.2 39.0 8.3Y 6.2/5.4
medium yellow 32.79 antique Brazil 74 -6.0 34.2 7.0Y 7.3/4.8
dark orange 18.60 antique Brazil 45 17.4 71.7 9.9YR 4.4/11.5
golden orange 18.98 pear Brazil 61 -1.0 42.0 4.3Y 6.0/6.0
golden orange 40.98 oval Brazil 50 -0.5 41.0 4.5Y 4.9/5.9
medium dark golden orange 3.90 emerald cut Africa 70 10.2 70.0 0.2Y 6.9/10.7
Morganite pink 17.33 square Brazil 81 4.6 -0.9 2.8RP 8.0/1.1
peach 6.92 square Brazil 80 10.4 10.0 9.7R 7.9/2.7
peach 9.06 oval Brazil 90 8.9 11.8 1.3YR 8.9/2.6
Brazilianite yellow-green 2.00 oval Brazil 74 -1.9 17.0 5.2Y 7.3/2.4
Cassiterite light brown 14.25 round Bolivia 47 7.5 26.6 9.3YR 4.6/4.3
yellow 2.88 round Bolivia 82 1.3 33.0 1.8Y 8.1/4.9
Calcite dark brown-orange 12.55 round Baja, Mexico 41 23.2 58.4 7.3YR 4.0/10.1
Gemstone Color Weight Shape Location L*a*b* Munsell
Calcite-Co dark rose pink 3.40 cushion Spain 20 47.4 -16.4 3.1RP 1.9/11.9
Childrenite peach 1.37 round Brazil 74 19.0 9.3 3.8R 7.3/4.5
Chrysoberyl
brownish-green 7.80 oval Sri Lanka 47 -3.6 28.8 6.7Y 4.6/4.0
medium-brown 6.19 oval Sri Lanka 38 5.8 36.3 1.3Y 3.7/5.4
brownish-yellow 7.51 round Sri Lanka 54 2.6 27.7 1.9Y 5.3/4.1
green-yellow 7.04 round Sri Lanka 54 -0.4 40.4 4.2Y 5.3/5.8
yellow-brown 11.84 oval Brazil 67 2.8 48.1 2.3Y 6.6/7.1
dark greenish-yellow 13.25 antique Brazil 49 -6.0 36.3 7.7Y 4.8/5.1
brown 9.30 emerald cut Sri Lanka 43 6.7 42.5 1.2Y 4.2/6.5
dark greenish-yellow 21.30 oval Sri Lanka 59 -4.9 31.3 7.0Y 5.8/4.4
lemon yellow 11.49 oval Brazil 72 -9.4 30.8 0.9GY 7.1/4.2
greenish-yellow 12.02 round Sri Lanka 50 -7.1 41.3 8.0Y 4.9/5.7
Chrysocolla medium blue 13.59 free form Arizona 39 -36.0 -9.5 5.9BG 3.8/7.4
Cinnabar red 1.37 fancy Charcas, Mexico 11 37.4 36.5 1.1YR 1.0/9.4
Clinohumite orange 1.52 emerald cut USSR 36 24.8 59.0 7.3YR 3.5/10.3
Corundum
Ruby Pink-violetish red 3.66 antique Thailand 23 40.9 -0.8 7.5RP 2.2/9.5
dark pinkish-red 3.56 oval Burma 24 48.0 -19.3 2.2RP 2.3/12.3
dark red 2.23 oval Thailand 19 44.0 -1.3 7.6RP 1.8/10.2
medium pinkish-red 2.30 oval Burma 49 45.8 -21.9 0.6RP 4.8/12.0
opink-orangy red 2.11 antique Thailand 26 46.2 2.4 8.5RP 2.5/10.7
medium red 2.07 antique Thailand 24 45.9 0.2 7.9RP 2.3/10.6
violetish-red 3.56 antique Thailand 18 42.5 -7.2 5.4RP 1.7/10.2
violetish-red 1.02 pear Thailand 38 38.8 -19.3 0.6RP 3.7/10.3
pinkish red 0.98 oval Thailand 37 50.5 -19.1 2.2RP 3.6/12.8
Sapphire light pink 2.12 oval Sri Lanka 23 19.6 -12.1 9.1P 2.2/5.1
medium purple- blue 3.76 antique Sri Lanka 38 21.7 -40.7 8.9PB 3.7/10.2
dark green 4.25 oval Sri Lanka 20 -11.6 11.5 8.2GY 1.9/2.4
fine medium dark blue 5.21 oval Sri Lanka 21 23.0 -48.2 7.6PB 2.0/12.1
medium blue 6.05 oval Sri Lanka 47 9.7 -30.9 7.4PB 4.6/7.3
dark blue 2.60 oval Sri Lanka 17 15.5 -39.0 7.0PB 1.6/9.7
violetish-pink 4.02 oval Sri Lanka 37 33.7 -21.8 8.5P 3.6/8.9
dark lemon yellow 16.12 oval Sri Lanka 70 -0.3 56.8 3.8Y 6.9/8.2
medium green 1.98 antique Umba Valley, Tanzania 52 -5.4 19.8 9.3Y 5.1/2.7
very pale yellow 1.40 antique Umba Valley, Tanzania 79 4.7 5.4 1.0YR 7.8/1.3
red-violet 1.86 emerald cut Umba Valley, Tanzania 34 7.2 -8.9 3.1P 3.3/2.5
orangy-yellow 3.41 antique Umba Valley, Tanzania 55 8.3 38.2 0.1Y 5.4/6.0
brown-pink 3.28 emerald cut Umba Valley, Tanzania 36 15.4 12.3 9.5R 3.5/3.7
orangy-red 0.96 antique Umba Valley, Tanzania 40 44.7 15.6 2.8R 3.9/10.5
blue-violet 3.77 antique Umba Valley, Tanzania 42 8.4 -19.3 8.7PB 4.1/4.6
green 1.46 round Umba Valley, Tanzania 55 -9.1 19.2 3.5GY 5.4/2.9
powder-blue 2.56 round Umba Valley, Tanzania 54 5.4 -23.3 6.9PB 5.3/5.5
brownish-orange 4.64 antique Umba Valley, Tanzania 30 33.7 35.6 1.1YR 2.9/8.9
Gemstone Color Weight Shape Location L*a*b* Munsell
Heated Geuda dark golden yellow 6.13 oval Sri Lanka 81 11.6 78.3 0.1y 8.0/12.1
medium orange 3.89 oval Sri Lanka 42 11.2 54.6 0.4Y 4.1/8.4
dark orange 4.00 oval Sri Lanka 53 31.5 92.3 7.3YR 5.2/15.7
yellow 2.21 oval Sri Lanka 80 8.0 78.3 1.0Y 7.9/11.9
orangy-yellow 3.60 oval Sri Lanka 58 11.4 70.0 0.7Y 5.7/10.7
Miscellaneous dark blue 3.87 emerald cut Austrlaia 15 8.7 -32.0 5.7PB 1.4/7.8
dark blue-green 5.75 emerald cut Austrlaia 18 -7.1 -7.3 2.5B 1.7/2.2
dark pink 6.2 oval Sri Lanka 52 25.8 -18.1 7.7P 5.1/7.0
dark blue Kahsmir 25 5.0 -25.0 5.4PB 2.4/6.0
beige-yellow 5.55 oval Sri Lanka 60 13.7 29.9 6.0YR 5.9/5.4
dark blue 2.3 pear Montana 28 -7.3 -8.4 4.0B 2.7/2.5
medium blue 1.35 octagon Montana 40 -6.0 -13.5 8.8B 3.9/3.6
medium light blue 1.19 pear Montana 52 0.9 -17.0 4.8PB 5.1/4.1
light blue 1.4 shield Montana 77 2.0 13.5 7.0PB 7.6/3.1
blue-green 1.47 pear Montana 48 -8.2 0.7 1.1BG 4.7/1.5
light yellow-green 1.77 pear Montana 75 -8.6 13.3 6.1GY 7.4/2.2
light greenish-yellow 1.66 shield Montana 70 -11.9 25.3 4.0GY 6.9/3.8
light green 1.10 octagon Montana 64 -4.0 13.3 0.1GY 6.3/1.8
yellow 0.95 shield Montana 70 -2.0 26.7 4.8Y 6.9/3.8
orange-mauve 0.96 shield Montana 58 5.8 5.8 0.6YR 5.7/1.5
beige 1.03 pear Montana 60 8.1 9.5 1.7YR 5.9/2.2
Creedite violet 0.96 emerald cut Mexico 60 15.7 -12.6 6.6P 5.9/4.4
Crocoite orangy-red 1.87 emerald cut Tasmania 33 50.0 75.0 3.0YR 3.2/15.8
Cuprite dark red 11.62 round South Africa 6 48.5 27.7 6.9R 0.9/11.1
Diaspore pale gray-yellow 2.1 emerald cut Turkey 69 -0.8 13.8 4.2Y 6.8/2.0
Diopside medium green 2.23 round New York 72 -3.5 15.6 7.6Y 7.1/2.2
     chrome dark green 0.75 round Kenya 36 -26.2 51.0 4.7GY 3.5/8.0
     chrome dark green 4.95 antique USSR 10 -18.0 35.7 3.5GY 0.9/5.5
Dioptase green 0.41 emerald cut Tsumeb, Namibia 28 -62.6 -1.2 1.5BG 2.7/12.0
Enstatite brown 0.52 round Burma 52 3.3 32.5 1.9Y 5.1/4.8
green 2.43 pear Africa 32 -20.2 54.0 2.4GY 3.1/7.8
light brown 4.38 emerald cut Africa 50 14.8 40.0 7.7YR 4.9/6.8
Epidote dark brown 3.43 cushion Africa 2 7.3 21.7 0.1Y 0.9/3.5
Euclase light blue- green 1.33 emerald cut Brazil 77 -4.6 0.0 3.6BG 7.6/0.9
dark blue 0.24 emerald cut Zimbabwe 35 -4.5 -20.4 0.8PB 3.4/5.0
Fluorite emerald-green 3.05 pear Colombia 59 -27.0 19.1 0.9G 5.8/5.3
pink 0.92 round Switzerland 70 18.4 6.8 2.0R 6.9/4.4
violet 5.75 round Illinois 17 20.3 25.1 1.8P 1.6/7.1
blue-green 6.05 oval England 44 -19.8 7.6 4.5G 4.3/3.6
yellow 8.80 round Illinois 62 0.1 49.8 3.8Y 6.1/7.2
blue 75.77 marquire Illinois 36 -2.8 31.3 2.2PB 3.5/7.6
Garnets
Andradite medium green 0.47 round Korea 50 -13.2 33.2 2.5GY 4.9/4.8
olive green 0.51 round Korea 47 0.3 40.3 4.2Y 4.6/5.8
brown 0.33 round East Siberia, USSR 29 15.6 44.3 8.9YR 2.8/7.4
Demantoid medium green 0.68 emerald cut USSR 51 -38.8 54.6 7.2GY 5.0//9.8
Grossular medium orange 9.81 round Asbestos, Quebec 44 14.4 28.0 5.9YR 4.3/5.2
light mint green 4.15 antique Tanzania 70 -11.9 19.6 5.8GY 6.9/3.2
light brownish-yellow 5.01 triangle Tanzania 55 6.3 32.9 0.1Y 5.4/5.1
light brownish-yellow 2.59 emerald cut Tanzania 84 9.4 38.9 8.2YR 8.3/6.3
cinnamon brown 4.48 antique Tanzania 51 19.6 17.9 10.0R 5.0/5.0
Gemstone Color Weight Shape Location L*a*b* Munsell
near colorless 2.18 round Tanzania 92 0.9 8.4 0.1Y 9.1/1.3
medium mint green 3.88 antique Tanzania 58 -16.8 23.0 6.9GY 5.7/4.1
dark green 2.47 emerald cut Tanzania (tsavorite) 50 -46.6 34.6 0.5G 4.9/9.2
dark orange 4.82 antique Tanzania 88 44.4 66.0 0.3YR 8.7/14.7
very pale green 4.14 antique Tanzania 77 2.9 4.6 3.5YR 7.6/0.9
Malaya medium brownish-orange 12.8 triangle Tanzania 30 25.6 24.6 0.6YR 2.9/6.5
brownish-pink 11.39 antique Tanzania 44 17.3 5.6 9.1R 4.3/1.7
orange 6.38 triangle Tanzania 45 16.9 30.7 5.3YR 4.4/5.9
gray-brown 8.23 antique Tanzania 39 8.0 20.6 8.0YR 3.8/3.5
pinkish-orange 8.56 antique Tanzania 48 19.1 21.3 1.3YR 4.7/5.2
dark orange 14.46 antique Tanzania 25 35.9 48.9 3.3YR 2.4/10.6
Pyrope
Almandine medium rose-pink 3.09 round Sri Lanka 28 36.7 1.8 8.3RP 2.7/8.5
light rose-pink 0.74 round North Carolina 54 -24.8 -5.7 3.4RP 5.3/6.0
dark red 0.58 round Arizona 23 33.5 38.4 2.1YR 2.2/9.0
brown-orange 1.27 round Mozambique 30 38.1 22.0 6.5R 2.9/8.9
brownish 6.48 emerald cut ? 26 38.6 28.4 8.5R 2.5/9.3
Rhodolite red-violet 10.88 oval Tanzania 12 22.5 -9.1 2.3RP 1.1/5.7
brownish-violet 13.10 round Tanzania 10 31.7 7.3 2.0R 0.9/7.3
fine dark violet 24.46 antique Tanzania 16 37.6 -4.8 6.0RP 1.5/9.0
Spessartine light orange 3.61 round Orissa,India 55 18.1 38.3 5.9YR 5.4/7.0
medium orange 3.81 round Orissa,India 45 29.1 55.8 5.2YR 4.4/10.6
dark orange 5.65 oval Orissa,India 22 34.2 54.2 4.7YR 2.1/10.8
Spessartine dark brownish-orange 4.05 pear Brazil 25 31.1 31.8 1.2YR 2.4/8.0
dark brownish-orange 15.40 emerald cut Madagascar 14 30.3 41.4 4.1YR 1.3/8.8
light orange 4.65 oval Amelia, Virginia 40 28.3 37.9 2.8YR 3.9/8.2
medium brownish-orange 6.41 antique ? 31 37.2 58.6 4.1YR 3.0/11.9
dark orange 1.27 round Africa 38 27.5 29.6 1.2YR 3.7/7.3
very dark brownish-orange 16.80 antique Brazil 4 26.5 26.7 2.0YR 0.9/6.7
light orange 1.75 round Ramona, Californnia 74 34.5 62.4 3.1YR 7.3/12.5
Tsavorite medium dark green 4.11 oval Tanzania 40 -49.0 32.4 1.0G 3.9/9.4
fine medium green 2.47 emerald cut Tanzania 50 -46.6 34.8 0.5G 4.9/9.2
medium green 1.25 emerald cut Tanzania 44 -47.2 27.8 1.6G 4.3/8.9
dark green 4.01 oval Tanzania 32 -51.8 32.6 1.1G 3.1/9.8
Haüyne blue 0.04 fancy Germany 52 1.0 -40.0 4.1PB 5.1/9.7
Hypersthene dark bottle green 2.52 pear Arizona 25 -6.0 41.7 8.1Y 2.4/5.7
Idocrase brown 2.30 round Africa 46 14.9 52.6 9.2YR 4.5/8.5
green 1.05 round Afirca 52 14.4 51.5 1.0GY 5.1/7.1
brown 3.82 emerald cut Switzerland 35 15.9 42.6 8.3YR 3.4/7.2
brown 1.40 cushion Itlay 51 6.6 67.0 2.4Y 5.0/9.9
Iolite blue 1.56 round India 28 10.7 -24.0 8.2PB 2.7/5.9
blue 3.00 emerald cut India 26 10.1 -25.3 7.6PB 2.5/6.1
Kornerupine light green 0.40 round Africa 65 -32.1 28.6 0.1G 6.4/6.7
    (chrome) light brown 12.07 round Sri Lanka 50 5.4 30.5 0.3Y 4.9/4.6
olivy-brown 2.62 oval Sri Lanka 34 1.0 19.7 5.5Y 3.3/2.8
Kyanite medium blue 8.30 cushion Brazil 48 -11.6 -21.7 7.9B 4.7/5.8
dark blue 4.01 cushion Brazil 40 1.0 -33.0 3.8PB 3.9/8.0
Lazulite blue 0.70 round Brazil 47 -6.1 -31.5 1.5PB 4.6/7.8
Microlite green 0.14 oval Brazil 59 -24.0 23.3 9.4GY 5.8/5.1
Manganotantalite red 4.85 cushion Mozambique 11 37.2 36.5 1.2YR 10./9.4
Opal yellow 11.74 emerald cut Idaho 49 5.5 59.3 2.5Y 4.8/8.7
brown-gray 5.15 round Mexico 35 0.7 12.7 3.2Y 3.4/1.8
Gemstone Color Weight Shape Location L*a*b* Munsell
orangy-red 0.76 round Mexico 46 50.9 95.4 4.0YR 4.5/18.6
light orange 8.04 oval Mexico 46 19.3 55.7 8.1YR 4.5/9.5
Peridot medium green 8.25 antique Arizona 47 -20.9 52.3 3.2GY 4.6/7.7
medium green 9.20 triangle Arizona 34 -11.9 48.5 0.1GY 3.3/6.6
light green 4.51 pear Norway 66 -19.0 31.7 5.9GY 6.5/5.2
light green 8.22 oval Egypt 58 -13.3 31.9 3.0GY 5.7/4.7
Phosphophyllite light blue-green 0.81 emerald cut Bolivia 85 -4.2 -1.4 9.8BG 8.4/0.9
Proustite dark red 2.58 round Germany 18 51.6 50.0 10.0R 1.7/13.5
Quartz
Amethyst lilac 6.22 emerald cut Brazil 57 19.4 -12.0 8.6P 5.6/5.0
light violet 9.18 oval Brazil 37 18.5 -14.5 7.1P 3.6/5.2
dark violet 8.52 fancy oval Zambia 6 25.5 -26.0 3.0P 0.9/8.0
medium dark violet 4.40 oval Brazil 6 22.8 -21.1 3.9P 0.9/6.9
medium dark violet 3.61 round Brazil 12 29.8 -29.0 3.3P 1.1/9.2
medium dark purple 6.41 round Brazil 14 20.1 -23.2 2.3P 1.3/6.8
dark purple 6.38 fancy emerald cut Brazil 12 25.9 -25.3 3.5P 1.1/8.0
“Siberian” 14.91 oval Para, Brazil 8 30.8 -23.4 7.8P 0.9/8.5
Citrine medium yellow-orange 7.55 round Brazil 52 13.5 43.1 8.4YR 5.1/7.1
brownish-orange 4.20 round Brazil 38 7.9 34.8 0.1Y 3.7/5.4
dark straw-yellow 8.81 oval Brazil 55 5.4 23.9 9.8YR 5.4/3.8
pale straw-yellow 12.64 oval Brazil 61 0.7 19.3 2.7Y 6.0/2.8
light orange 16.90 antique Brazil 56 12.1 61.0 0.1Y 5.5/9.5
medium orange 19.72 oval Brazil 53 19.2 66.5 8.7YR 5.2/10.9
dark orange 15.76 oval Brazil 33 21.7 51.1 7.4YR 3.2/8.9
dark orange 15.33 oval Brazil 29 30.5 61.1 6.3YR 2.7/11.3
     (“Madeira”)
Green quartz apple green 4.48 oval Brazil 52 -9.5 13.0 6.5GY 5.1/2.3
Rose Quartz medium pink 14.2 emerald cut Brazil 51 13.1 4.2 2.0R 5.0/3.1
pale pink 18.79 antique Brazil 71 6.0 6.1 0.2YR 7.0/1.5
Smoky Quartz medium brown 23.78 round Brazil 26 7.6 12.3 5.6YR 2.5/2.4
light brown 15.61 emerald cut Brazil 63 4.5 23.7 0.1Y 6.2/3.7
medium yellow-brown 9.37 emerald cut Brazil 43 5.6 22.5 0.1Y 4.2/3.5
dark brown 13.57 emerald cut Brazil 20 8.6 15.1 6.5YR 1.9/2.8
very dark brown 7.49 emerald cut Brazil 1 6.8 11.6 6.6YR 0.9/2.2
Rhodochrosite pink 11.88 antique Colorado 39 40.2 11.4 1.8R 3.8/9.4
pink 7.15 rhomboid Peru 51 42.1 11.9 1.3R 5.0/9.9
orangy-red 9.42 round South Africa 30 52.7 52.3 10.0R 2.9/14.0
pink 3.95 round Argentina 49 37.6 15.6 3.5R 4.8/8.8
red 24.60 antique South Africa 16 43.6 44.9 1.2YR 1.5/11.4
Scapolite gold-yellow 32.44 oval Tanzania 67 3.0 55.4 2.5Y 6.6/8.1
gold-yellow 32.00 antique Tanzania 53 3.2 53.7 3.0Y 5.2/7.9
very pale yellow 5.77 antique Brazil 76 -1.8 11.8 5.9Y 5.2/7.9
lemon yellow 9.03 antique Burma 61 1.0 37.0 3.1Y 6.0/5.4
violet 4.36 oval Tanzania 30 16.1 -16.2 4.2P 2.9/5.0
Scheelite straw yellow 2.85 pear Korea 84 0.0 30.3 2.5Y 8.3/4.4
Scorodite violet-blue 1.15 fancy Namibia 23 5.7 -13.4 8.0PB 2.2/3.3
violet-blue 1.50 pear Namibia 15 5.3 -26.8 4.9PB 1.4/6.6
Sinhalite dark straw-yellow 4.58 antique Sri Lanka 50 6.6 32.5 0.1Y 4.9/5.1
brown 7.07 oval Sri Lanka 16 16.7 37.6 8.1YR 1.5/6.5
green 4.18 oval Sri Lanka 47 1.0 25.6 3.2Y 4.6/3.7
yellow 9.18 oval Sri Lanka 65 8.9 37.0 9.1YR 6.4/5.9
Smithsonite pale yellow 8.00 round Namibia 75 4.2 9.0 5.6YR 7.4/1.6
beige 10.40 oval Namibia 73 1.3 6.0 9.3YR 7.2/0.9
Gemstone Color Weight Shape Location L*a*b* Munsell
Sodalite intense dark blue 0.85 emerald cut Namibia 23 20.0 43.2 7.7PB 2.2/10.8
Sphalerite light green 1.93 round Colorado 68 -2.8 73.4 5.1Y 6.7/10.4
yellow-orange 3.30 round Spain 72 6.9 100 2.7Y 7.1/14.7
dark green 4.65 round Mexico 43 0.6 55.0 4.6Y 4.2/7.9
dark orange 14.48 round Spain 39 38.1 86.6 6.3YR 3.8/15.5
light orange 5.57 round Spain 55 26.6 10.3 2.9R 5.4/6.3
Sphene brownish yellow-green 6.22 emerald cut Madagascar 49 2.3 66.9 4.0Y 4.8/9.7
light yellow-green 1.55 round Baja, Mexico 73 -10.8 56.2 8.1Y 7.2/7.8
light brown 1.76 round Baja, Mexico 28 21.2 51.0 7.9YR 2.7/8.9
medium green 7.01 emerald cut India 34 -17.5 47.5 2.3GY 3.3/6.9
emerald green 1.01 round Baja, Mexico 24 -33.3 34.2 8.5GY 2.3/7.2
brown 1.44 round Baja, Mexico 60 11.9 80.4 1.0Y 5.9/12.3
yellow-green 4.22 round India 51 -1.3 67.8 5.2Y 5.0/9.6
yellow 2.65 antique India 79 -5.8 74.9 5.7Y 7.8/10.5
Spinel
Blues dark blue 8.35 oval Sri Lanka 12 -0.6 -12.7 2.1PB 1.1/3.1
medium dark blue 9.20 oval Sri Lanka 15 -6.9 -12.7 6.2B 1.4/3.3
light blue 9.30 oval Sri Lanka 31 -6.6 -11.9 7.2B 3.0/3.2
lavender-blue 15.22 oval Sri Lanka 50 4.8 -16.8 7.5PB 4.9/3.9
greenish-blue 4.78 round Sri Lanka 21 -13.6 -11.1 0.7B 2.0/3.8
cobalt-blue 11.23 emerald cut Sri Lanka 6 -2.3 -19.7 0.8PB 0.9/4.8
slightly violetish-blue 7.27 round Sri Lanka 29 2.8 -20.8 4.8PB 2.8/5.1
dark violet 5.46 antique Sri Lanka 13 5.2 -13.7 7.2PB 1.2/3.4
magenta 3.96 oval Sri Lanka 19 44.4 -4.5 6.3RP 1.8/10.6
medium purple 11.98 antique Sri Lanka 14 7.2 -9.2 2.0P 1.3/2.5
blue-violet 8.53 oval Sri Lanka 25 6.0 -12.6 8.6PB 2.4/3.1
;ight purple 7.98 oval Sri Lanka 27 14.4 -9.0 9.0P 2.6/3.7
gray-blue 14.96 antique Sri Lanka 30 -5.1 -8.5 6.9B 2.9/2.3
Pinks dark rose-red 8.21 round Sri Lanka 14 27.0 2.4 9.3RP 1.3/6.3
light rose-red 7.65 oval Sri Lanka 30 25.3 -0.7 7.1RP2.9/5.8
dark pink 5.23 oval Burma 24 -24.8 -4.8 4.7RP 2.3/6.0
dark violetish-red 9.02 oval Sri Lanka 21 19.3 -2.2 5.9RP 2.0/4.6
medium reddish-purple 7.07 oval Sri Lanka 26 27.1 -6.8 3.9RP 2.5/6.6
grayish-pink 5.89 oval Sri Lanka 47 21.4 2.0 8.1RP 4.6/4.9
medium pink 6.56 oval USSR 68 41.6 3.8 7.4RP 6.7/9.7
slightly bluish-pink 8.87 oval Sri Lanka 42 15.4 -2.5 4.5RP 4.1/3.7
light dusty -pink 11.4 antique Burma 54 16.2 -2.8 4.1RP 5.3/3.9
Reds dark orangy-red 5.30 round Burma 27 24.7 20.7 10.0R 2.6/6.0
medium pinkish-orange 2.98 oval Burma 41 43.5 10.4 0.9R 4.0/10.3
medium brownish-pink 3.07 round Burma 42 34.5 7.8 0.7R 4.1/8.2
medium brown 2.34 round Burma 45 26.4 14.4 5.7R 4.4/6.2
light brownish-pink 10.98 oval Burma 48 23.6 8.1 2.4R 4.7/5.5
dark grayish-pink 3.95 round Burma 31 14.7 4.1 2.0R 3.0/3.4
dark red 8.89 oval Burma 8 36.8 31.8 0.2YR 0.9/9.1
medium red 2.68 oval Burma 30 41.5 25.1 6.8R 2.9/9.7
medium pinkish-red 3.21 round Burma 27 47.5 7.4 0.1R 2.5/11.1
Spodumene blue 29.85 oval Brazil 53 -2.7 -3.4 6.7B 5.2/1.0
medium pink 16.06 emerald cut Afghanistan 59 -17.7 12.9 2.3B 5.8/4.8
medium pink 17.76 oval California 58 19.1 -10.9 9.1P 5.7/4.8
yellow-green 17.01 emerald cut Afghanistan 63 -5.3 28.0 7.5Y 6.2/3.9
dark pink 47.33 oval Brazil 65 32.2 -19.0 8.7P 6.4/8.3
Gemstone Color Weight Shape Location L*a*b* Munsell
Taaffeite gray-mauve 1.60 rhomboid Sri Lanka 50 4.5 0.8 9.0RP 4.9/1.0
Topaz yellow-brown 6.72 round USSR 38 13.0 37.2 8.6YR 3.7/6.2
red-orange 12.59 emerald cut Brazil 49 38.6 37.5 9.9R 4.8/10.1
dark beige 5.29 round Mexico 56 12.0 26.3 6.2YR 5.5/4.8
yellow 4.65 oval Brazil 59 8.6 27.7 8.3YR 5.8/4.6
dark orange 25.25 oval Brazil 61 23.9 61.5 6.6YR 6.0/10.8
brownish-pink 8.76 antique Brazil 63 35.0 5.7 8.6RP 6.2/8.2
medium blue 7.2 oval Brazil 60 -14.3 -17.6 6.1B 5.9/5.2
red-orange 8.45 antique Brazil 65 34.4 26.8 7.6R 6.4/8.7
medium pink 17.84 oval USSR 73 25.2 -16.9 7.7P 7.2/6.7
Tourmaline
Rubellite pinkish-orange 36.85 emerald cut Madagacar 25 38.3 21.2 6.4R 2.4/8.9
dark red-violet 13.16 oval Brazil 24 47.8 -0.9 7.6RP 2.3/11.1
very dark violet-red 17.13 emerald cut Brazil 5 28.0 2.8 9.6RP 0.9/6.5
medium violet 16.73 antique Brazil 20 38.1 -5.0 5.8RP 1.9/9.1
dark red 10.26 antique Ouro Fino, Brazil 12 39.5 7.4 0.1R 1.1/9.1
dark pinkish-red 36.56 emerald cut Brazil 19 41.8 10.4 2.0R  1.8/9.7
Blues and Greens intense smalt blue 9.84 emerald cut Brazil 41 -21.0 18.8 9.6GY 4.0/4.3
blue-green 15.96 emerald cut Brazil 50 -40.1 -0.1 2.3BG 4.9/7.7
fine green 10.05 triangle Africa 30 30.7 23.9 0.1G 2.9/6.0
   (chrome)
slightly yellowish-green 9.68 emerald cut Brazil 52 -39.7 15.9 3.9G 5.1/7.3
dark green 14.75 emerald cut Brazil 32 -38.8 31.1 0.1G 3.1/7.7
Orangy Colors peachy-orange 10.90 round Mozambique 42 31.1 20.5 7.2R 4.1/7.4
medium brownish-orange 5.74 antique Tanzania 43 18.6 56.6 8.5YR 4.2/9.4
dark brownish-orange 4.84 round Tanzania 48 20.9 70.4 8.7YR 4.7/11.6
medium orangy-brown 10.39 oval Tanzania 28 10.7 46.0 0.4Y 2.7/7.1
medium pinkish-brown 46.84 oval Tanzania 31 24.0 26.4 1.8YR 3.0/6.4
Pinks medium pink 32.32 oval Afghanistan 57 34.7 0.0 6.5RP 5.6/8.2
medium dark rose-pink 10.95 round Brazil 28 34.0 -4.2 5.6RP 2.7/8.1
slightly brownish-pink 11.13 antique Mozambique 44 28.7 12.5 4.1R 4.3/6.6
brown-pink 21.22 emerald cut Stewart Mine, Pala California 38 18.7 20.6 1.7YR 3.7/5.0
Mozambique medium pinkish-beige 2.51 round Mozambique 66 23.7 7.7 1.4R 6.5/5.6
Color Suite light pinkish-beige 2.37 round Mozambique 78 19.1 5.5 0.4R 7.7/5.6
near colorless 2.59 round Mozambique 85 7.9 3.9 3.5R 8.4/1.9
light pink 2.19 round Mozambique 56 33.2 -5.7 4.1RP 5.5/8.0
dark rose-pink 2.15 round Mozambique 35 47.0 -11.6 3.9RP 3.4/11.5
dark green 2.16 round Mozambique 24 -12.8 22.0 4.6GY 2.3/3/5
dark brownish-green 2.34 round Mozambique 34 -14.7 37.0 2.4GY 3.3/5.4
medium green 2.68 round Mozambique 52 -8.3 41.4 8.5Y 5.1/5.7
lime green 2.10 round Mozambique 64 -8.6 26.0 1.2GY 6.3/3.7
very pale green 3.08 round Mozambique 69 0.1 12.8 2.9Y 6.8/1.8
colorless 2.22 round Mozambique 84 1.5 2.1 2.3YR 8.3/0.4
beige-yellow 2.04 round Mozambique 87 3.8 21.6 9.3YR 8.6/3.4
light brown 2.33 round Mozambique 37 9.0 51.1 1.2Y 3.6/7.8
dark brown 1.81 round Mozambique 36 18.9 33.8 5.6YR 3.5/6.4
blue 2.30 round Mozambique 45 -8.4 -2.1 6.2BG 4.4/1.7
Gemstone Color Weight Shape Location L*a*b* Munsell
Willemite golden yellow 2.35 pear Franklin, New Jersey 85 -7.4 63.0 6.2Y 8.4/8.9
Wulfenite yellow 6.11 oval Namibia 63 1.0 29.0 2.8Y 6.2/4.2
orangy-red 2.54 emerald cut Red Cloud Mine, Arizona 45 43.8 96.1 5.4YR 4.4/17.6
Zircon reddish-brown 19.03 oval Sri Lanka 17 16.2 16.7 2.2YR 1.6/4.1
brownish-yellow 17.43 oval Sri Lanka 37 12.2 49.6 0.1Y 3.6/7.8
violet-rose 14.20 round Sri Lanka 20 30.9 3.4 9.4RP 1.9/7.2
dark orange 9.26 oval Sri Lanka 33 25.5 66.0 7.9YR 3.2/11.4
green 4.36 oval Sri Lanka 48 -15.4 25.8 5.4GY 4.7/4.2
rose-red 11.26 emerald cut Sri Lanka 19 26.2 8.3 3.1R 1.8/5.9
lemon yellow 15.70 oval Sri Lanka 50 -0.3 31.6 4.2Y 4.9/4.5
medium blue 5.56 oval Cambodia 46 -12.3 -14.1 4.9B 4.5/4.2
yellow 8.92 oval Sri Lanka 65 10.8 58.1 0.1Y 6.4/9.0
pale gray-green 16.63 antique Sri Lanka 66 7.8 14.6 5.4YR 5.4/2.7
reddish-brown 7.77 oval Sri Lanka 26 23.0 29.1 3.2YR 3.5/6.5
light olive green 5.34 round Sri Lanka 47 -0.3 19.2 4.3Y 4.6/2.7
dark blue 2.87 round Cambodia 56 -8.4 -11.1 6.8B 5.5/3.3
light pink 1.36 round Sri Lanka 71 11.9 -5.8 0.7B 7.0/2.8
light orange 1.44 round Sri Lanka 59 26.2 58.1 5.7YR 5.8/10.6
medium orange 2.59 round Sri Lanka 52 39.4 70.9 4.0YR 5.1/13.9
pale blue-green 2.67 round Cambodia 77 -6.9 -1.4 7.2BG 7.6/1.4
Zoisite violet-blue 26.54 pear Tanzania 20 55.0 -76.3 8.6PB 1.9/20.9
light blue-gray 1.06 round Tanzania 75 0.7 0.6 9.5R 7.4/0.1
medium blue 2.3 round Tanzania 60 3.5 -20.7 6.4PB 5.9/4.8
violet-blue 0.96 emerald cut Tanzania 47 16.8 -35.7 8.8PB 4.6/8.7
brown-blue 0.92 emerald cut Tanzania 61 7.1 -11.7 2.0P 6.0/3.0

Editor’s Note: The IGS gratefully acknowledges the above as the work of Dr. Joel Arem. We are deeply grateful to him for allowing us to re-purpose this content with attribution.

About the author
Joel E. Arem, Ph.D., FGA
Dr. Joel E. Arem has more than 60 years of experience in the world of gems and minerals. After obtaining his Ph.D. in Mineralogy from Harvard University, he has published numerous books that are still among the most widely used references and guidebooks on crystals, gems and minerals in the world. Co-founder and President of numerous organizations, Dr. Arem has enjoyed a lifelong career in mineralogy and gemology. He has been a Smithsonian scientist and Curator, a consultant to many well-known companies and institutions, and a prolific author and speaker. Although his main activities have been as a gem cutter and dealer, his focus has always been education.
All articles by this author