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The Opal
Chemical Composition and Mineralization of Opals
Opal is an amorphous quartz composed of silica anhydride and water (SiO² + H²O); as a colloidal substance, it lacks a crystalline structure and has no regular form. Opal often appears in mammillated, reniform, or stalactitic formations. It is monorefractive, with a low refractive index, which can occasionally be abnormal or birefringent. Its luster ranges from vitreous to greasy, resinous, or waxy. Perfect transparency is found only in the hyalite variety, and its density is much lower than that of crystalline quartz, resulting in lower hardness, although its optical properties are not significantly different.
Opal does not possess a crystalline structure, although it has a minimum reticular order with variable entities. Very fragile, opal can develop very fine conchoidal fractures if it loses water rapidly. Its vitreous luster is subdued, opalescent, and often milky. In translucent white-blue varieties, it displays opalescence and iridescence due to refraction, possibly resulting from a fine lamellar structure or a microstructure of internal silica spheres (found in noble opal, which is absent in our environment). In semi-opal varieties, its color ranges from brownish to black, even in highly acidic environments.
In general, opal represents a metastable phase of chalcedony. This means that it slowly transforms through crystallization and loses water over time. This occurs naturally through a process of aging over relatively short geological timescales. Poor-quality opal likely originates from a type of silica with a different history, transported directly from below by later hydrothermal fluids rich in silica.
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The Symbolism of Opal
According to an earlier positive tradition, opal was thought to possess significant powers. It was said to bring kindness and courtesy, combat melancholy, and bestow love, happiness, and inner strength, especially when Venus was well-placed in the wearer's horoscope. Opal was believed to protect against misfortune, becoming opaque as a warning and breaking if misfortune was averted. It is a stone of loyalty and spirituality, tenderness, and trust.
The black variety, according to the ancients, is especially beneficial and brings more luck than others. In summary, opal is considered the most beneficial gem, believed to encompass the virtues of all other stones. However, an old saying holds that "Every opal wearer is in the hands of God and need not fear any illness." Like diamond, opal is thought to turn against the wicked and dishonorable, revealing all ills to those who wear it unworthily; hence, it came to be viewed, as mentioned, as a cursed gem.
Opal and Its Virtues
Benefits for the Body
Physically, opal is believed to be beneficial for eye health. It strengthens vision and is associated with all eye disorders. It also supports the health of nails, hair, and skin. Opal balances fluids in the body, making it valuable against water retention. It is said to purify the kidneys and blood and regulate insulin production. Additionally, it stimulates memory and balances female hormones.
Mental Benefits
Opal helps enhance emotions and bring feelings to the surface for examination. It amplifies the process of healing past wounds and clears away old resentments. Use it if you wish to be more positive and spontaneous with others. It is said to bring happiness and a playful change.
On an Energetic Level
Opal stimulates all seven chakras. According to its color, it brings energy and positive vibrations to the corresponding chakra. It also works within the aura, balancing it. Opal awakens psychic and mystical qualities. It has historically been used to induce dreams and lucid vision. It attracts angelic entities and enhances communication with the Divine.
The Different Types of Opals
Noble opal is milky, semi-transparent, and clearly shows the iridescent phenomenon, sometimes evenly, sometimes in spots or streaks. The hues are often pearl gray or blue but can also appear colored.
Harlequin opal, for example, has many patches packed together, resembling the patches that make up the traditional costume of Bergamo's Harlequin. Flame opal has a striped iridescence, and sunflower opal shows blue and golden reflections. The most significant noble opal deposits are found in the Czech Republic, Germany, Mexico, England, and Australia.
Black Opal
Black opal has a deep color and can be opaque with some translucency, especially when exposed to intense light. "Gray opal" is rarely used as a name; specimens of this variety are generally included in the "Black" or "Dark" category, distinguished by a translucent to opaque gray body. Its composition is: SiO2 + H2O + C, Fe (carbon and iron).
White Opal
White opal, also known as "Opale Chiaro," is a very popular and trendy gem. It can be translucent or opaque with a white body. White opal is characterized by an opaque milky background, with colors that can be very vivid and bright. In opal classification, the white tone is identified by N9. The mines around the mining town of Coober Pedy in South Australia are the primary source of this precious opal.
Welo Opal
Welo Opal has an electric neon color with different patterns on a predominantly white body, though some specimens are yellow or amber. Welo Opal is found in quartz veins at a depth of 2 to 3 meters below the surface. Its extraction is challenging due to the methods used. This stone was discovered in the Semien Wollo mountainous region in northeastern Ethiopia.
It stands out for its bright color and wonderful transparency. Welo Opal also captivates with its shifting reflections, displaying all the colors of the rainbow, especially yellow, orange, red, and green. Welo Opal can contain up to 8% water by weight. Additionally, the hardness of Welo Opal on the Mohs scale ranges from 5.5 to 6.5. Therefore, a Welo Opal should not be worn near quartz or other harder stones, as they might scratch it.
Gelatin Opal
Gelatin Opal can be transparent or translucent, and due to the lack of a host rock or background color, or if it has one, it is called “Crystal Opal,” “White Crystal Opal,” “Dark Crystal Opal,” or “Black Crystal Opal.” Opaque opals with matrix (host rock) included in the cut are called "boulder opals"; each opal with visible host rock on the front is referred to as “Opals with Matrix.”
Fire Opal
Not all opals display a play of color. Fire Opal is a transparent crystal opal or translucent, lacking a color play but instead showcasing beautiful shades of orange, red, yellow, and sometimes blue or brown.
The red and green reflections in these opals resemble the warmth of a flame. They are often found in volcanic or sedimentary rocks or in secondary deposits produced by erosion, particularly in Australia. Fire Opal is even more beautiful than noble opal but sensitive to external influences: air, light, temperature, and water. When exposed to these, it tends to crack and turn milky, losing the beautiful reflections that are its most distinctive feature. The most common shape for this stone is a curved surface cut; however, fire opal can also be multifaceted with a satisfying aesthetic effect. Buriti Fire Opal is mined in Brazil and enchants with its red and orange colors, resembling Mexican Fire Opal.
Boulder Opal
Boulder Opal from Queensland is characterized by various shapes and colors on smooth or rough surfaces. In this case, opal is found as a coating on a rock matrix. Peruvian Opal is a rare variety featuring beautiful translucent blues, pinks, and greens without any play of color. Another colorless variety is the translucent yellow and green opal found in Tanzania.
How to Choose Your Opal ?
How to Recognize a Genuine Stone
As many may know, a simple way to differentiate is by temperature, as fake stones are warmer than real ones. Natural stones are heavy, hard to degrade, and have characteristic veins absent in fake stones. Additionally, the structure is another distinguishing feature: fake stones lack clarity and do not contain quartz or calcite crystals, essential elements in nature.
Beware of Fake Stones!
Don't be fooled; make sure the crystal you're purchasing isn't "fake." Unfortunately, the rarity of some stones, like fire opal, leads some honest vendors to sell trinkets made of glass and plastic or less expensive altered stones sold as others. In many cases, you can spot a fake because rare and valuable stones are often sold cheaply in small village shops.
The brilliance of the opal is fundamental, and the lighter the color, the higher its value. Brightness is classified into four levels:
- Level 1: Barely visible, almost absent in color reproduction, even under bright light.
- Level 2: Shows some color, but the colors are bright, even under lighting.
- Level 3: Vibrant and very colorful, with brightness increasing under direct sunlight.
- Level 4: Very bright, clear, with vivid color visible in both direct and indirect light.
And How Do Jewelers Identify Gemstones?
In short, a gemstone is recognized by its imperfections and veins (use a magnifying glass to observe these). But even for experts, it’s not always easy. A trained eye is useful, and for precious stones such as diamond, ruby, sapphire, and emerald, thorough examinations are conducted.
Is Opal a Precious Stone?
Opal is one of the most delicate stones, easily marked and highly sensitive to temperature changes. Being a hydrated silicate, it can be damaged in very dry environments. It is recommended to occasionally submerge it in water. Do not use oils or detergents to clean your opal jewelry.