Amethyst

The vivid purple and violet tones of amethyst are primarily attributed to the presence of iron impurities within the crystal structure of silicon dioxide (SiO₂), the mineral composition of quartz. Specifically, the presence of tetravalent iron (Fe⁴⁺) impurities is largely responsible for the distinctive coloration of amethyst.

During the formation of amethyst, naturally occurring gamma radiation can induce a transformation of trivalent iron (Fe³⁺) to tetravalent iron (Fe⁴⁺). This process occurs within the crystal lattice structure as the quartz undergoes crystallization. The tetravalent iron impurities absorb specific wavelengths of light, resulting in the characteristic purple and violet hues observed in amethyst.

However, the stability of the tetravalent iron state in amethyst is inherently fragile, particularly under 'normal' surface conditions, such as exposure to sunlight. Prolonged exposure to natural sunlight can trigger a reversible process wherein the tetravalent iron reverts back to the trivalent state. This reversal of oxidation states leads to a loss of the vivid purple coloration, causing the amethyst to fade over time when exposed to sunlight.

While other impurities may exist in amethyst, such as manganese, aluminum, or titanium, they typically have less significant contributions to the overall coloration of the gem stone compared to tetravalent iron. Therefore, the presence and oxidation state of iron impurities, particularly Fe⁴⁺, play a predominant role in determining the color intensity and stability of amethyst. Understanding the role of tetravalent iron impurities in amethyst not only sheds light on the origin of its distinctive color but also explains why prolonged exposure to sunlight can cause the gem stone to lose its vibrant hues.

Display

Amethyst, particularly in the form of large cathedrals or geodes, is meant to be showcased and admired. However, it's essential to note that amethyst can experience fading over time, with the duration varying widely from a few months to as long as 10+ years, making it difficult to predict.

My recommendation is to proudly display cathedrals and pieces from Brazil or Uruguay in your home. Avoid placing them directly in front of windows or exposing them to outdoor elements. Instead, indirect sunlight will allow you to enjoy them for years without significant fading.

Vera Cruz amethyst, often utilized in jewelry or showcased as specimens, originates from various regional mines, each exhibiting its unique fading characteristics. While some may fade quickly, others take longer to show signs of fading.

Amethyst is abundant worldwide, found in locations ranging from our British Columbia Okanagan region to Russia, remote sites in Arizona, Oregon, and beyond. This abundance is attributed to its composition, primarily consisting of silica, oxygen, and traces of iron, which are among the most prevalent elements in the Earth's crust.

Although the fade time frame can be greatly influenced by the locale where the amethyst is sourced, South American varieties, which dominate the global market, generally fare well as long as they are shielded from direct sunlight.

Spodumene (Kunzite, Hiddenite, Triphane)

Spodumene, a mineral variety encompassing three distinct types—Kunzite, Hiddenite, and Triphane—is highly prone to fading, often at a rapid pace. While there are certain locations where fading is not typical, such as the Hiddenite found in the southern USA, there are instances where crystals remain unfaded despite neighboring ones in pegmatite formations fading. However, discerning which pockets or sites are resistant to color fading and which are not appears to be a matter of chance or lacks comprehensive documentation. The only way to ascertain this is by exposing the crystal and observing the outcome, though unfortunately, this often results in undesirable changes. Spodumene that has undergone artificial irradiation is particularly susceptible to rapid fading. Personal experiences include instances where Brazilian hiddenites faded back to clear within as little as two months, despite being shielded from direct sunlight and kept away from windows in a windowless room.

Display

I suggest storing valuable spodumenes in an opaque container, avoiding glass or plastic. Opt for a wooden display with a solid door, or wrap them securely in cloth to prevent any light from penetrating. If the crystal is inexpensive, it's advisable to expose it, wear it, and replace it as necessary.

Kunzite, the variety commonly used in jewelry, is often referred to as 'the evening stone' precisely because it's recommended not to wear it during the daytime, thus minimizing long-term exposure to sunlight.

Fluorapatite

Coming Soon

Display

While I lack sufficient experience with fluorapatite to offer specific display recommendations, my intuition suggests that it does not require an opaque box for storage. Like many minerals discussed here, it likely only needs to be kept away from direct sunlight to maintain its integrity.

Fluorite

Fluorite presents a complex scenario due to the vast array of specimens originating from various locations. Commercial grade polished varieties like Chinese rainbow fluorites can maintain their color for a prolonged period if shielded from direct sunlight. Madagascar green fluorites are notably resilient to direct sunlight exposure and can withstand it for extended durations. However, purple fluorites sourced from multiple locations, including Mexico, Morocco, Tennessee, Illinois, and China, are prone to color fading with light exposure. Similarly, greens and blues from around the world are not significantly more resilient. Despite their susceptibility to fading, fluorites are generally not a cause for excessive concern. Unlike spodumenes, most fluorites, whether used in jewelry or as specimens, will retain their color for several years without noticeable fading. With proper display conditions, such as being kept away from direct sunlight, they can easily last a decade or longer.

Fluorites are prevalent in beginner and novice fluorescent mineral displays. It's essential to note that exposure to direct artificial UV light can significantly accelerate fading. While the crystal may still exhibit vibrant fluorescence, the daylight coloration may become less saturated over time.

Display

To reduce color fading in fluorite specimens, it's best to store them in a dimly lit area away from direct sunlight. While it may be tempting to display them in windowsills to showcase their translucency, prolonged exposure to sunlight can accelerate color fading. However, if kept out of direct sunlight, fluorite colors can remain vibrant for many years.

Vivianite

Vivianite is known for its tendency to darken upon exposure to light and air, rather than undergo a color change to shades of brown, yellow, or colorless. This darkening process is attributed to the oxidation of iron ions within the mineral's structure. As a result, vivianite specimens may gradually develop a darker, more opaque appearance over time.

It's essential to clarify that while vivianite can darken with exposure to light and air, the extent and rate of this darkening may vary depending on factors such as environmental conditions and the specific properties of the specimen.

Display

One positive aspect of vivianite is that its color remains stable and does not fade. However, it's essential to keep this specimen away from direct sunlight to prevent any unnecessary changes. Despite its sensitivity to air, which may cause the crystals to darken over time, they retain their green hue.In my view, despite any darkening, the specimens retain their stunning allure and deserve to be displayed prominently.

Topaz

Not all topaz varieties are prone to fading; in fact, many are quite stable. However, one notable exception is the topaz sourced from Topaz Mountain, Utah. At this location, even just walking around the site, one can observe numerous shards and pieces of topaz glittering in the dirt. However, over time, these visible pieces have all transitioned from an amber or champagne hue to clear. It's believed that direct sunlight exposure at this location can cause the crystals to fade within a single season.

Display

This non-jewelry grade topaz should be treated as a specimen only and kept away from direct sunlight to preserve its condition. While it doesn't require an opaque enclosure, it's important to ensure it's shielded from direct sunlight to maintain its integrity.

Scapolite

When buying scapolite, it's crucial to discern whether the color is natural or artificially induced, as heat-treated or irradiated specimens may fade when exposed to heat and light. Natural specimens, on the other hand, will maintain their color without fading. Be particularly inquisitive about purple specimens.

Display

Since I exclusively purchase naturally colored scapolite, I lack sufficient knowledge about the time frame for fading to offer a recommendation.

Coquimbite

This beautiful and rare purple mineral will not hold up well to sunlight.

Display

This obscure Italian stone should be shielded from direct sunlight and ideally kept in an opaque display. It's best to take it out for viewing or showcasing as necessary.

Pink Halite

Impurities, such as iron oxide and potassium, contribute to pink halite fading, especially under UV light exposure. When exposed to light, these impurities undergo chemical reactions, altering the halite's color and causing it to fade over time. While iron oxide is a significant factor, other impurities and environmental conditions also affect fading. Pink halite, notably from California, is highly prone to UV-induced fading, with crystals reverting to a clear state over time. Despite some fluorescence, UV light exposure accelerates this process. Thus, collectors should take precautions to minimize UV exposure, particularly for specimens from California.

Display

This crystal will retain its color, so long as it is stored away from direct sunlight.