Turquoise is a popular gemstone known for its striking blue-green color. It has been prized for thousands of years by cultures around the world. The variation in turquoise color is part of what makes this gemstone so intriguing. Turquoise can range from sky blue to greenish robin’s egg blue, to pale green. The most valuable and desirable turquoise gemstones exhibit a strong, evenly distributed, blue-to-blue green color. This article will examine the factors that impact turquoise color and value, and discuss which shade of turquoise is considered the most valuable by gemologists and collectors.
What Causes the Color Variation in Turquoise?
Turquoise gets its distinctive color from traces of copper. The intensity and balance of blue and green hues depends on the amount of copper, as well as the presence of other minerals in the stone. The major factors that affect turquoise color are:
Copper Content
Higher copper content produces a stronger, vivid blue color. Stones with less copper take on more green tones. The most valuable turquoise has a rich, evenly distributed blue caused by higher copper content.
Matrix
The matrix refers to the webbed veins that run through turquoise stones. These are made of other minerals like quartz, pyrite, and limonite. The matrix can block or dilute the blue color if it takes up more surface area. Matrix-free turquoise or stones with thin matrix achieve better color saturation.
Color Distribution
Uniform color distribution is ideal. Mottled or uneven turquoise with blotchy patches of color is considered less valuable. High quality turquoise will exhibit an evenly distributed blue-green color across the entire surface.
Source Material
The composition of the original rock where turquoise formed also impacts color. Some sources have more favorable mineral mixes to produce deep blue turquoise. Source mines known for vivid color include Persia, Arizona, and New Mexico.
What is Robin’s Egg Blue Turquoise?
Robin’s egg blue is a pale shade of blue-green associated with the eggs laid by robins. It is lighter and brighter than the standard turquoise hue. The name became linked with turquoise since it accurately describes the distinctive pastel blue-green color of the gemstone.
Robin’s egg blue turquoise is characterized by:
– Pale, soft blue-green color
– Higher amounts of iron, zinc, and aluminum minerals
– Lower copper content than typical turquoise
– Frequently occurs in softer, porous stones
This delicate color is created when turquoise lacks the full intensity of blue caused by high copper content. It remains popular for its distinctive pale green-blue shade.
How Does Color Affect Turquoise Value?
The most important factor influencing a turquoise gemstone’s value is its color. Deep blue turquoise is considered the most valuable and sought-after by collectors and jewelers. Here are the key considerations when evaluating turquoise value based on color:
Blue Hue
A strong blue color, rather than green, increases turquoise value. Medium to deep sky blue is ideal. Pale green-blue is less desirable.
Color Saturation
Vivid, concentrated color is best. Pale or washed out turquoise with weak color intensity is cheaper.
Color Distribution
An even, uniform blue-green color across the stone is preferred. Mottled or blotchy turquoise is lower quality.
Matrix
Thin matrix increases color showing through. Thick, dense webs of matrix reduce value by interrupting color.
Natural vs. Treated
Natural turquoise commands higher prices. Treated stones to enhance color are less valuable.
| Turquoise Color | Value Level |
|---|---|
| Deep “Persian” blue | Most Valuable |
| Sky blue | High Value |
| Blue-green | Medium Value |
| Sea green | Lower Value |
| Pale “Robin’s egg” blue | Least Valuable |
What are the Most Valuable Turquoise Colors?
Based on the factors that drive turquoise value, the most valuable and desirable shades are:
Persian Blue
The deepest, brightest blue turquoise is sometimes called “Persian blue” after the vividly colored stones mined in Persia (modern day Iran). This tone has the highest copper content and strongest blue saturation. Good quality Persian blue turquoise is very rare and commands premium prices.
Sky Blue
Slightly lighter sky blue turquoise is also highly valued. It exhibits an evenly distributed, pure blue hue ranging from Dodger blue to azure blue. Like Persian blue, high quality sky blue turquoise is becoming increasingly hard to find.
Blue-Green
As blue tones shift towards a blue-green balance, value decreases somewhat. Rich blue-green turquoise is still a high quality color, especially with strong color distribution. Stones from Arizona’s Sleeping Beauty mine offer an ideal example of desirable blue-green turquoise.
How is Turquoise Color Enhanced?
Natural turquoise color can be altered through treatments to improve or intensify color. Common turquoise color enhancement techniques include:
Stabilization
Oils, waxes, plastic resins, and waterglass are used to penetrate porous turquoise to harden it and evenly distribute color. This reduces the chalky appearance of untreated porous stones.
Dyeing
Turquoise is submerged in dye solutions to add or alter color. Common dyes for turquoise include Prussian blue, methyl violet, and methylene blue. This produces unnatural uniform color.
Bleaching
Bleaching oxidizes the copper in turquoise, turning green hues more blue. Peroxide and acid solutions draw out discoloration to brighten tone.
Irradiation
Exposure to gamma rays or neutron radiation alters minerals in turquoise to change color. Irradiation can improve greenish turquoise but lead to instability.
Waxing
Clear, colorless waxes are used to coat turquoise and deepen sky blue tones. Waxing is also used to seal color after dying.
Identifying Enhanced Turquoise Color
Natural turquoise commands higher value than treated stones. Here are some signs that a turquoise gem has artificial color enhancement:
– Uniform “robin’s egg” blue uncommon in natural turquoise
– Fluorescent chalky appearance under UV light
– Excessively vivid electric blue color
– Presence of wax filler, plastics, or resins
– Signs of instability like crumbling, cracking, or fading
Reputable sellers will disclose any turquoise color treatments. Untreated natural turquoise with authentic color is the most prized by collectors.
Conclusion
The striking color range of turquoise makes it a unique and captivating gemstone. Shade impacts turquoise value, with deep blue tones being the most valuable and sought-after. The rarest and most expensive turquoise exhibits a natural vivid Persian blue or sky blue color. Evenly distributed color without matrix also increases desirability. While artificial treatments can enhance turquoise, natural stones command higher prices. For both beauty and value, gem quality turquoise in deeper shades of blue remains the most precious.
