Amber is a golden yellow to orange-brown color that has been valued since ancient times. The name “amber” comes from the Arabic word anbar, meaning ambergris. Ambergris is a waxy substance produced by sperm whales and was historically used in perfumes. The aromatic qualities of ambergris led to the use of the word amber being applied to describe the golden fossilized tree resin that was also widely used in antiquity. Today amber commonly refers to the fossilized tree resin, not ambergris.
Amber ranges in color from golden yellow to orange-brown due to differences in composition and oxidation. The most desirable and valuable amber is a bright transparent yellow. However, amber also occurs in an opaque form and can be found in a variety of shades including yellow, orange, red, brown, green, blue, and even black. The variability in amber color leads many to wonder, what is considered the proper color for amber?
What Causes the Range of Amber Colors?
Amber is formed from the fossilized resin of ancient conifer trees. The resin secreted by these trees served to seal wounds and protect the tree. This resin contained a complex mixture of organic compounds including labdanoid diterpenes, carotenoid pigments, and volatile oils. When the resin was exuded and exposed to air it began to harden. Over millions of years, the resin was buried under sediment and subjected to heat and pressure which caused the volatile components to polymerize. This process transformed the resin into the hardened fossilized material we know as amber.
The exact chemical composition of the original conifer resin determines the color and properties of the resulting amber. Differences in the original botanical source of the resin and subsequent changes during fossilization such as oxidation lead to the wide range of potential colors.
The key factors that influence amber color are:
| Factor | Effect on Color |
|---|---|
| Botanical source | The type of ancient conifer tree affects compounds present |
| Composition | Ratio of labdanoid diterpenes to carotenoid pigments |
| Oxidation | Exposure to oxygen can cause darkening |
| Impurities | Inorganics like sulfur cause discoloration |
| Treatment | Heating, irradiation, oils alter appearance |
Carotenoid pigments are one of the major factors producing the golden and orange hues of amber. These organic plant compounds are also found in many living plants today and are what give vegetables like carrots and squash their vibrant colors. The specific carotenoid composition affects the exact shade. Limonene, a cyclic terpene, is thought to contribute to amber’s yellow hues. Labdanoid diterpenes, including communol, communic acid, and copalic acid, are amber constituents that can oxidize over time leading to darker more orange-brown shades. Impurities like sulfur also promote discoloration.
Grading Scales for Amber
Since not all amber is the same color, grading scales were developed to categorize amber based on its appearance. These standardized scales assign amber samples into color grades ranging from the palest yellow to darkest orange-brown. The grades are then associated with quality, transparency, and value.
Some common amber grading scales include:
Gemological Institute of America
| Grade | Color |
|---|---|
| Extra light | Very pale yellow |
| Light | Pale yellow |
| Medium light | Golden yellow |
| Medium | Golden yellow |
| Medium dark | Yellowish orange |
| Dark | Reddish orange |
Russian Amber Grading System
| Grade | Color |
|---|---|
| 0 | Very light, transparent |
| 1 | Light yellow, transparent |
| 2 | Light yellow, translucent |
| 3 | Yellow, semitransparent |
| 4 | Yellow, almost opaque |
| 5 | Yellow, opaque |
| 6 | Yellow-brown, opaque |
| 7 | Brown, opaque |
Blue Amber Scale
| Grade | Color |
|---|---|
| 1A | Very pale yellow |
| 2A | Pale yellow |
| 3A | Butter yellow |
| 4A | Golden yellow |
| 5A | Deep yellow |
| 6A | Orange yellow |
| 7A | Reddish orange |
| 8A | Reddish brown |
While the exact scales differ, the trend is consistent across grading systems. The palest yellow amber is given the highest grades while dark opaque amber is assigned the lowest grades. Intermediate colors span the spectrum from light yellow to reddish-orange. The amber with medium golden hues ranks the highest in most grading scales.
Standard Amber Colors in Jewelry
When it comes to jewelry, the most common and sought-after amber is a light to medium transparent golden yellow. This warm yellow amber is considered the “classic” jewelry grade amber. It has enough color to show the prized golden hue yet remains translucent. Darker opaque amber is typically less desirable for jewelry purposes.
Standard amber colors used in jewelry can be summarized as:
| Amber Color | Description |
|---|---|
| Golden | Light to medium yellow-orange |
| Butter | Very light creamy yellow |
| Cherry | Ruby red-brown opaque amber |
| Green | Rare greenish amber |
| Black | Opaque dark amber |
The most popular is golden amber with its warm yellow-orange tones. Butter amber has a very delicate light yellow color. Cherry and black refer to the darker opaque amber that has reddish-brown and blackish-brown hues. Green amber is very rare but derives its color from small gas bubbles in the resin.
Ideal Amber Color for Insects
Amber that contains perfectly preserved insect inclusions is highly prized by collectors. The amber color ideal for showcasing insect specimens differs from jewelry-grade amber. The preferred color is a clear light yellow or yellow-orange. Darker amber obscures details of the insects. The clarity and purity of color allow the fine features of the insects to be displayed and backlit. Heavily included or cloudy amber is less desirable. Baltic amber from the Baltic Sea region often exhibits exquisite plant and animal inclusions.
Properties Determining Amber Color
The color of amber is directly influenced by its unique composition and properties. The key characteristics that determine its color include:
| Property | Effect on Color |
|---|---|
| Transparency | Clear transparent amber transmits light better revealing a brighter yellow color. |
| Inclusions | Foreign particles can block and scatter light causing a murky appearance. |
| Oxidation | Exposure to oxygen causes chemical changes darkening the color over time. |
| Treatment | Heating, oils, and resins impact light absorption and color. |
| Origin | The botanical source affects the compounds responsible for color. |
The highest quality amber is transparent and free of inclusions. This allows the passage of light and amplification of the yellow-orange hues. Opaque amber appears darker because the light is scattered by internal imperfections. Oxidation and exposure to chemicals like oils and alcohols also intensify the color. Untreated natural amber generally exhibits the purest and lightest yellow shades. The original botanical origin also determines the presence of yellow pigments.
Recent Spectroscopy Studies on Amber
Modern analytical techniques like spectroscopy have provided new insights into the chemical factors producing amber’s range of colors. Here are some findings from recent spectroscopic research:
- Infrared spectroscopy showed more carbonyl groups in darker amber indicating greater oxidation.
- UV-visible spectroscopy revealed absorbing carotenoids are responsible for yellow-orange colors.
- Fluorescence spectroscopy found energy transfer from tree resins caused an amber color shift.
- Raman spectroscopy detected higher levels of conjugated C=C double bonds in darker samples.
These studies confirm that amber’s color diversity stems from differences in composition as certain compounds will selectively absorb or transmit specific wavelengths of light. Spectroscopy has allowed the identification of chromophore groups that contribute to color intensity. This helps explain why some amber remains beautifully golden while other specimens turn darker.
Finding the True Color of Amber
Determining the true inherent color of amber can be challenging since many factors can alter its appearance. Here are some tips for observing the natural color:
- Examine in transmitted daylight – sunlight passing through amber reveals its clearest color.
- Inspect raw untreated samples – heating, oils, and handling can slightly darken amber.
- Review recently excavated material – fresh amber hasn’t been exposed to years of oxidation.
- Evaluate interior fractured surfaces – broken areas avoid weathered exteriors.
- Consider country of origin – some regions yield lighter yellow amber.
Analyzing freshly collected samples away from direct light exposure provides the best indication of amber’s original pale yellow to golden yellow hues characteristic when initially formed from ancient tree resin.
Conclusion
Amber spans a spectrum of golden yellow to orange-brown colors due to the complex chemistry of ancient plant resins. The most desirable and purest colors are light transparent yellows exhibiting a brilliant golden tone. While oxidation and natural processing can darken amber over geological time, newly uncovered samples still reflect their initial bright yellowish hue. Modern spectroscopy has uncovered the specific pigments and chemical bonding patterns underlying amber’s diverse palette. When properly assessed, the true inherent color of amber derives from its origins as a fresh golden yellow tree resin undergoing gradual transformation.
