Opal is a gemstone of varying colors and transparency, as well as its chemical composition which cannot be determined by a definite formula, as the mineral’s water content varies depending on the deposit’s location and depth. Opal is a colloidal substance composed of amorphous silica in which traces of calcium, magnesium, aluminum, iron and uranium are present.
chemical composition and mineralization of opales
Opal is an amorphous quartz composed of silica anhydride and water SiO² + H²O; being a colloidal substance, it has no crystalline structure and is lacking a regular shape. The opal generally appears under the aspect of mammary, reniform or stalactite incrustations. Monorefractory, with a low refractive index, can sometimes be abnormal, birefringent. It has a vitreous sheen tending towards fat, resin or wax. Perfect transparency as in the hyalite variety, density much lower than crystalline quartz and therefore hardness, but the optical properties are not so different.
It does not have a crystalline structure, although it has a minimal reticular order with variable entity. Very fragile, if it rapidly loses water, the opal can be filled with very small concoidal fractures. Its vitreous luster is weak, opalescent and often milky; in the translucent white-blue varieties, it is opalescent and iridescent by refraction, perhaps because of a fine lamellar structure or a microstructure of internal silica spheres (noble opal, absent in our environment); in the semi-opal variety, it passes from brownish to black, even in a very acidic environment.
Typically, opal represents a metastable phase of chalcedony, i.e. it slowly transforms by crystallizing and losing water with a natural aging process in relatively short geological times. Poor opal would likely come from a silica with a different history, transported directly from the downstream by later silica-rich hydrothermal fluids.
The symbol of Opale
This curious gem is a symbol of hope, purity, peace and obedience, especially in the East where it is considered a sacred stone, an emblem of excellence and faithfulness. In ancient times, the opal was so linked to law and justice that it was supposed to punish villains; but the course of the centuries changed its destiny and it ended up becoming, in certain religions, a symbol of the cunning stone and protector of thieves. More widely, especially in the eighteenth century, the opal began to be seen as a bearer of bad luck and all the virtues it was accused of in the past were denied. It is believed that during the plague, which scourged Venice during this time, the cause of the infection was attributed to the stone.
According to an earlier positive tradition, the opal would be loaded with powers: it would give kindness and courtesy, fight against melancholy, give love, happiness, inner strength, beauty, especially when the planet Venus is well placed in the wearer’s horoscope. It was said to protect against misfortunes, and became opaque to announce them and break them when they were thwarted. It is a stone of fidelity and religiosity, of tenderness and trust.
The black variety, the ancients claim, is very beneficial and brings luck more than others. In short, opal would be the beneficial gem of excellence because it includes the virtues of all the others. But this is not exactly the maxim that states: “Every opal wearer is in the hands of God and should not fear any disease”. Like the diamond, it also changes favor towards the wicked and unworthy, thus revealing itself to these bearers of all evils, from then on it was transformed, as mentioned, into a diabolical jewel.
Opal and its virtues
Opal encourages valuing and consideration of the emotional, sentimental and joyful aspects of life, bringing joy, happiness and enthusiasm in times of melancholy. Communicating exuberance, striving to rejoice in the happy aspects of life and thus dispelling worries; opens access to one’s emotions and stimulates confidence in the future. Opal balances imagination, creativity and poetry on the logical-rational side, functioning as a balancer.
Benefits for the body
On a physical level, opal is, needless to say, perhaps most valuable for eye health. Opal enhances vision and is associated with all eye disorders. It is also used for nail, hair and skin health. It balances fluids in the body and is therefore very valuable against water retention. It is said to purify the kidneys and blood, while regulating insulin production. Stimulates memory and balances female hormones.
Benefits for the mind
Opal helps to strengthen emotions, bringing feelings to the surface so they can be analyzed. It enhances the cleansing process of past wounds and erases old grievances. Use it if you want to be more positive and spontaneous with others. It brings happiness and a playful change.
Au niveau énergétique
It stimulates the seven chakras. Depending on the color, it brings energy and positive vibrations to the corresponding chakra. It also works within the aura by balancing it. Awaken your psychic and mystical qualities. It was used to induce lucid dreams and vision. It attracts angelic entities and improves communication with the Divine. It helps to connect to the forces of water.
The different types of opals
The noble opal is whitish, milky, semi-transparent and clearly shows the irization phenomenon, now uniform, now by dots and stripes. The drapes are often pearl gray or blue, but can also be colored.
Harlequin opal, for example, has numerous macules packed together, like the proverbial patches that make up the Bergamo mask dress; the flame has a striped iridescence; the one known as sunflower shows blue and gold reflections. The most important noble opal deposits are found in the Czech Republic, Germany, Mexico, England and Australia.
Black opal has a black ground color and can be opaque with some translucency, especially when exposed to an intense light source. Gray opal is a rarely used name: specimens of this variety are usually included in the “Black” or “Dark” category, but are distinguished by a translucent to opaque gray body. Its composition is as follows: SiO2 + H2O + C, Fe (carbon and iron), color: black, iridescent.
White opal, also called “Opal Chiaro“, is a very popular and fashionable gem. It can be translucent or opaque with a white body. White opal is characterized by a milky opaque background and the colors can be very bright and vivid. In the classification of opals, the white tone is identified by N9. The mines located around the mining town of Coober Pedy, in the state of South Australia, are the primary source for this valuable opal.
Welo Opal has an electric neon color and different patterns on a predominantly white body, although some specimens are yellow or amber. Welo opal is found in quartz veins at a depth of 2 to 3 meters below the surface. The difficulty of its extraction is mainly due to the methods used. This stone was discovered in the mountainous region “Semien Wollo” in northeastern Ethiopia.
It is distinguished by its bright and shiny color and its wonderful transparency. Welo opal also enchants with its changing reflections that show all the rainbow colors, especially yellow, orange, red and green. Welo opal can be composed of water up to 8% of its weight. And another interesting aspect is that the hardness of the opal is on the Mohs scale between the values of 5.5 and 6.5. Therefore, a Welo opal should not be approached or worn with quartz or other harder stones, such as beryl, corundum and diamond. Your Welo opal could be scratched by the harder stones.
Gelatin opal can be transparent or translucent and, due to the absence of the parent rock or without background color, or if it is positive, it is called “Crystal Opal”, “White Crystal Opal”, “Dark Crystal Opal” or “Black Crystal Opal”. Opals that are opaque with a matrix (host rock) included in the cut are called pebble opals; each opal with a visible host rock in front is called “Opals with matrix”.
But not all opals have a color scheme. Fire Opal is a transparent or translucent opal crystal with no interplay of color, where instead it shows wonderful shades of orange, red, yellow and even blue or brown.
The red and green reflections remind in this type the warmth of the flame. It is generally found in eruptive or sedimentary rocks, or in secondary deposits produced by the erosion of the latter, especially in Australia. Fire opal is even more beautiful than the noble and sensitive to external influences: air, light, temperature, water. Subjected to these, tends to crack and become milky, losing the beautiful reflections that are its most prominent feature. The most common form, for this stone, is the curved cut surface; the fire variety, however, can also be multiform with a satisfactory aesthetic result. Buriti fire opal is mined in Brazil and enchants with its red and orange colors, reminiscent of Mexican fire opal.
Boulder opal, from Queensland, is characterized by different shapes and colors on smooth or blunt surfaces. The opal in this case is found as a coating on a rock matrix. Peruvian Opal is a rare variety that has beautiful translucent blues, pinks and greens, without color schemes. Another variety without color scheme is the translucent yellow and green opal from Tanzania.
How to choose your opal?
When choosing an opal, the main factors to consider are size, color, brightness and quality of reflection. There are many types of stones and crystals. Choosing the right one is not easy, especially if you don’t know what you need at that particular moment. There are several ways to choose a stone. You may focus on a crystal because you want something with certain energetic properties, you may be attracted by its outward appearance (color, shape, size, etc.) or because it is connected to your zodiac sign. First and foremost, however, you need to make sure that the stone is real.
How to recognize if a stone is real
As many may know, a first distinction is made by temperature; fake stones are warmer than real ones. Natural stones are heavy, difficult to degrade and have characteristic veins that are absent in fake ones. In addition, the structure represents another distinctive characteristic: the fake stone does not have lucidity, nor quartz crystals or calcite in its structure, essential elements in nature.
Beware of fake stones!
Don’t be fooled and make sure that the crystal you buy is not “fake”. Unfortunately, the fact that some stones are quite difficult to find, such as fire opal, leads some honest dealers to buy glass and plastic trinkets or much cheaper modified stones that are marketed for others. In many cases, it will be possible to recognize the deception because, especially at village counters, they will tend to sell a very rare and expensive stone at bargain prices.
In general, the parity, the opal size usually determines the price which is measured in carats. The brilliance of the opal is of paramount importance and the lighter the color, the greater the value. Brightness is classified into 4 levels:
- Level 1: Little apparent almost absent in color reproduction, even under very bright light.
- Level 2: Shows some color, but the colors are vivid, even under bright lights
- Level 3: Bright, very colorful, but brighter in the classification of the lamp in direct sunlight.
- Level 4: Very bright, clear and showing good bright color in direct and indirect light.
How do goldsmiths recognize gemstones?
In short, a gemstone is known for its imperfections and veins (use a magnifying glass to observe them). But even for experts, it is not so easy, a trained eye is useful and for gems considered as diamond, ruby, sapphire, emerald examinations are made.
Is opal a gemstone?
Opal is cut mainly in cabochon if it is opaque or semi-transparent, faceted if it is transparent. Double opals (colorless quartz or glass on which a layer of opal is glued) are quite common. Opal can be treated with colored impregnating agents to darken the background color or colorless to enhance iridescence and conceal cracks in the surface. The most valuable variety is the noble opal, predominantly milky and white, tending to heaven, with a marked iridescence: from certain carats, these gems can reach high prices.
Opal is one of the most delicate stones, is easily marked and is very sensitive to temperature changes. Being a hydrated silicate, a very dry environment can damage it. It is therefore advisable to immerse it in water from time to time. Do not use oils or detergents to clean your opal ring.
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