Natural turquoise does change color over time, a phenomenon that is a defining characteristic of the untreated gemstone. This alteration is often referred to as developing a patina or discoloration. Turquoise is chemically defined as a hydrous phosphate of copper and aluminum, a composition that makes it uniquely susceptible to environmental factors. The gradual shift in hue, typically from a vibrant blue toward a darker or greener shade, is a natural interaction between the stone and its surroundings. This change is an indication of its genuine, untreated nature.
The Core Reason: Why Natural Turquoise is Vulnerable
The reason for turquoise’s color shift lies in its inherent physical and chemical structure. Natural turquoise is a comparatively soft material, generally rating between 5 and 6 on the Mohs scale of mineral hardness. This relatively low hardness is paired with a highly porous structure, meaning the stone contains tiny, interconnected openings. This porosity allows the stone to readily absorb substances it comes into contact with, acting much like a sponge. Turquoise is also a hydrous mineral, meaning its chemical formula includes water molecules. Changes in the stone’s hydration level, such as dehydration caused by heat, can affect its optical properties and consequently its color. The absorption of foreign materials into the pores then creates a chemical interaction with these internal elements, leading to the visible color change.
Primary Environmental Triggers of Discoloration
The most common cause of discoloration is the absorption of oils and cosmetic products from the wearer’s skin. Natural body oils, lotions, moisturizers, and even makeup can seep into the stone’s porous surface. Over time, these absorbed materials can cause the blue copper compounds in the stone to oxidize, resulting in a noticeable shift toward a darker or greenish hue.
Exposure to heat and light also serves as a trigger for color alteration. Prolonged or intense exposure to direct sunlight or high temperatures can cause the stone to dehydrate, leading to fading or a dulling of its original color. In some cases, extreme heat has been known to cause the blue stone to become greener.
Chemical exposure presents another risk, as household cleaners, chlorine from swimming pools, and acidic substances can catalyze irreversible chemical reactions within the stone. These substances can degrade the surface or penetrate the pores, leading to permanent changes in the stone’s color and texture. Acids in sweat or perfumes, for example, can react with the stone’s composition.
Protecting and Maintaining Natural Turquoise Jewelry
Preventative wearing habits are the most effective way to safeguard the color of natural turquoise jewelry. It is advisable to put on turquoise pieces only after applying cosmetics, perfumes, and hairspray, allowing those products to dry first. Similarly, the jewelry should be removed before engaging in activities that involve sweat, water exposure, or chemical contact, such as swimming, bathing, or cleaning.
Proper cleaning procedures for natural turquoise must be gentle to avoid driving foreign substances deeper into the stone. The stone should never be submerged in water, chemical cleaners, or an ultrasonic cleaner, as the liquid will be absorbed by the porous material. Instead, the stone should be gently wiped with a soft, dry cloth to remove surface oils and dust after wearing.
Safe storage is important for preventing both color change and physical damage. Turquoise should be stored separately from harder gemstones like diamonds or sapphires to prevent scratching its softer surface. The storage location should be cool and dry, away from direct heat sources or prolonged sunlight exposure.
Understanding Stabilized and Treated Turquoise
Because much of the turquoise mined is too soft or porous for jewelry use, a significant portion is subjected to stabilization treatments. Stabilization is a process where the porous stone is infused with a clear epoxy or resin, often under pressure and heat. This resin fills the voids, hardening the stone and sealing its surface.
The primary effect of stabilization is that the stone’s porosity is dramatically reduced, making it far more resistant to color change. Stabilized turquoise is much less susceptible to the absorption of skin oils, lotions, and household chemicals than its natural counterpart. This treatment effectively “locks in” the color, allowing the piece to maintain its appearance.
Other common treatments also affect the stone’s reaction. Color enhancement involves using dyes to achieve a more vibrant hue, and this altered material may fade when exposed to strong light or household chemicals. Reconstituted turquoise is made by grinding low-grade stone into a powder, mixing it with colored resin, and pressing it into blocks, which makes the final product behave more like a plastic than a natural stone.