Gemstone Color Measurements and Specifications

The Limitations of Color-Chart Systems for Gemstone Color Measurements

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.

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 or tone, 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.

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.

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 20^th 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.

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.

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

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

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	Myanmar	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	Russia	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	Myanmar	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	Myanmar	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	Russia	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	Myanmar	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, Russia	29	15.6	44.3	8.9YR 2.8/7.4
Demantoid	medium green	0.68	emerald cut	Russia	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
	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	Myanmar	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	Myanmar	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	Russia	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	Myanmar	54	16.2	-2.8	4.1RP 5.3/3.9
Reds	dark orangy-red	5.30	round	Myanmar	27	24.7	20.7	10.0R 2.6/6.0
	medium pinkish-orange	2.98	oval	Myanmar	41	43.5	10.4	0.9R 4.0/10.3
	medium brownish-pink	3.07	round	Myanmar	42	34.5	7.8	0.7R 4.1/8.2
	medium brown	2.34	round	Myanmar	45	26.4	14.4	5.7R 4.4/6.2
	light brownish-pink	10.98	oval	Myanmar	48	23.6	8.1	2.4R 4.7/5.5
	dark grayish-pink	3.95	round	Myanmar	31	14.7	4.1	2.0R 3.0/3.4
	dark red	8.89	oval	Myanmar	8	36.8	31.8	0.2YR 0.9/9.1
	medium red	2.68	oval	Myanmar	30	41.5	25.1	6.8R 2.9/9.7
	medium pinkish-red	3.21	round	Myanmar	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	Russia	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	Russia	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.