White Spots on Your Turquoise After Wear? An In-depth Analysis of the Three Main Causes and How to Solve It!
Since ancient times, people have seen the development and prosperity of jewelry and jade as inseparable from culture. It’s well known that in China, warm and gentle jade is highly sought after, while in other countries, bright and sparkling colored gemstones, such as turquoise, are more popular, making it important to understand issues like Turquoise White Spots and how to address them.
Turquoise has been known around the world for a long time, crossing borders. People have used this gemstone as adornment for over 5,000 years.
Today, turquoise is a beloved collectible and beaded accessory in China, while abroad, it’s a favorite material for high-end jewelry and a darling of designers.
Recently, a fan asked Peonyjewels: “I bought a piece of turquoise, and after wearing it for a while, I found some ‘white spots.’ What’s going on?” Don’t worry! This article has the answers you need.
Understanding Turquoise: From Mineral to Color
In gemology, turquoise is a hydrous copper aluminum phosphate mineral. It’s commonly blue-green and often accompanied by fine white lines, spots, brownish-black web-like veins (iron matrix), or dark mineral impurities.
Turquoise Colors
Natural turquoise can be divided into three main color categories: blue, green, and variegated. Common colors range from light to medium blue, and from greenish-blue to green. Varieties like sky blue, dark blue, light blue, bluish-green, green, yellowish-green, and light green are all common.
In China, people further categorize turquoise into commercial varieties based on color, such as “sky blue,” “blue-white,” and “rapeseed yellow.”
Turquoise Categories: Quality Determines Value
In gemology, experts determine the main categories of turquoise by color, texture, and density.
- Porcelain Turquoise:Porcelain Turquoise This is high-quality, dense turquoise with good color. It takes a strong polish and has high hardness, making it a premium variety. People consider the sky-blue color the best and often call it “Beauty Turquoise,” representing the highest grade.
- Green Turquoise: This type is relatively common, with colors ranging from bluish-green to pea-green. It has good density, polish, and hardness, making it a medium-quality turquoise.
- Iron Matrix Turquoise:When oxidized iron veins form a web-like or permeated pattern within the turquoise, people call it iron matrix turquoise. While pieces with average patterns have moderate value, people consider those with beautiful, intricate patterns “Wulan Hua” in China, and they hold significant market value.
- Chalky Turquoise (Porous Turquoise): This is the lowest quality turquoise, with colors often being pale off-white or light bluish-white. Its texture is loose, and it has a poor luster, low hardness, and low density. This type of turquoise often requires artificial treatment (like waxing or plastic impregnation) to improve its quality.
The Three Main Causes of Turquoise White Spots
The appearance of white spots on a turquoise stone can be traced to one of three reasons, regardless of the stone’s color or category.
1. Natural Mineral Inclusions: A Cause of Turquoise White Spots
Natural turquoise often contains fine, irregular white veins and patches on its blue or green base. Kaolinite and quartz are examples of these white mineral aggregates. In medium-to-low quality turquoise, you often find coexisting minerals like kaolinite, quartz, mica, and limonite. The proportion of these minerals directly affects the turquoise’s quality.
These types of white spots are inherent to the stone itself. More severe cases are known as mineral blemishes, and they will not change color with wear. A visible color difference will always remain.
2. High-Heat Dehydration During Polishing
While many turquoise roughs are flawless, white spots can appear after they are processed into finished products. High-heat dehydration during the polishing process often causes this. However, you can polish these spots away later with wear.
The surface and interior of turquoise contain water. Excessive friction during grinding and polishing generates high temperatures, causing the turquoise to lose water in localized areas. These dehydrated areas appear as uneven white spots on the surface. They typically disappear with continued wear and the formation of a patina.
The Role of Water in Minerals
To understand this, you need a little mineralogy. We categorize the water in minerals into three types based on its structure: adsorbed water, crystallization water, and structural water.
- Adsorbed Water: As the name suggests, this is water on the surface and in the cracks of the mineral. It’s like holding a bucket of water—it’s easily lost through dehydration. Opal is a prime example; it can dehydrate at just 100-125°C. In dry environments, African water opal can even lose water at room temperature.
- Crystallization Water: This water exists in the large gaps within the crystal structure. Its content is fixed, and it isn’t easily lost, requiring temperatures of 200-500°C. Dehydration will cause the structure to change. Gypsum and turquoise are typical examples.
- Structural Water: The most firmly held form of water in a gemstone, it exists as ions within the crystal structure. Its location and content are fixed, and it is extremely stable, making it very difficult to dehydrate. This requires 600-1000°C, and dehydration would completely alter the structure.
Turquoise can contain both crystallization water and adsorbed water. High-density porcelain turquoise contains structural water within its crystal lattice. Some lower-density turquoise, however, has many pores on its surface where adsorbed water can be present in the gaps between the crystal grains. When the stone absorbs this water, it looks better, but when it evaporates, the stone returns to its pale, lightweight, and dull state. This is what we call adsorbed water.
This explains the mystery: because its water content isn’t completely stable, turquoise can lose unstable water in its structure if the temperature gets too high during grinding and polishing, leading to the appearance of white spots.
3. Alkaline Reactions from Wear: Leading to Turquoise White Spots
Some pieces of turquoise may develop white spots gradually during wear, even if they looked perfect when purchased. This is often an alkaline reaction, mostly caused by prolonged contact with sweat. You can wear an alkaline reaction away with continued use.
Criteria for Judging High-Quality Turquoise
For beginners and outsiders, the value of turquoise can be confusing. Some pieces are very affordable, while high-quality, professional-grade stones are prohibitively expensive.
- Color：Color is a crucial factor in evaluating turquoise. High-quality turquoise should have a pure, clean, uniform, and vibrant color. The best color is sky blue, followed by deep blue, bluish-green, green, gray, and yellow.
- Clarity： Turquoise often comes with white fine lines, spots, brownish-black mineral impurities, clay minerals, and calcite. These impurities not only affect its aesthetic appeal but also its durability during processing and wear.
- Density and Hardness： High-quality turquoise has a dense structure with high density (around 2.7g/cm³) and hardness (a Mohs hardness of about 6).
- Pattern： Provided the turquoise has good density and polish, if the iron matrix forms a beautiful pattern, it can increase its value. People also know this as “Wulan Hua“.
- Stone Size： People mostly find turquoise roughs in small chunks or nodules, with most weighing under 50g. Assuming the same quality, the larger the piece of turquoise, the higher its price.
A Word from Peonyjewels
Whether for beaded accessories or high-end jewelry, turquoise stands out among other gemstones with its fresh, beautiful color and excellent versatility.
Though beautiful, the turquoise market is indeed complex and full of pitfalls. For general consumers, it’s essential to understand before you buy, and learn before you shop. For more expert tips and to see our collection, check out our unique handmade vintage earrings and other jewelry.
In the next article, we’ll share more tips on how to identify and understand turquoise.
