Here at Western Opals we are humbled to offer the highest quality specimens matched with real knowledge of opals and the many qualities they have to offer. We are passionate and available to answer any and all questions you might have about which opal is most suitable for you given your intention for working with this special stone. Please enjoy part 2 of Inside the World of Opals!
From Queretaro to Magdalena, the Opal Story Unfolds
In the late 1950s, Alfonso Ramirez of Querétaro discovered, supposedly on accident, the first opal mine in Jalisco. This mine was near the small town of Magdalena about 50 miles northwest of Guadalajara. He opened the first mine, La Única, located on the outer area of the volcano of Tequila.
It didn’t take long for prospectors and miners to migrate from Querétaro to Magdalena. Other deposits were discovered in the municipality of Magdalena (Las Latillas, La Mora, San Simón, Las Cruces, San Martín, El Huaxical and El Cabon being but a few of the early mines.) By 1960 hundreds of mines existed around the small town of Magdalena.
Opal Mining: Big Risk, Big Reward
Opal mining is a risky business. With the cost of buying and operating the heavy equipment, and paying the miners, one can very soon go broke if opal is not found.
Opal mines are open cast mines which requires a bulldozer and a backhoe. The opal forms when water seeps into silica-rich lava, filling seams and hollows. Under heat and pressure, the silica forms a solid gel that traps the remaining water within its structure. Small pebbles of fire opal are found embedded in lava flows. Fire opal was born in fire in the ancient volcanoes of Mexico, the story of the alchemy of fire and water over millions of years.
A small charge of dynamite is often used to break up the rhyolite rock. The opal is in pockets and seams in the rock. Ranging from transparent to translucent in appearance, Mexican opals have their own following in the world of gemstone collectors and aficionados.
Assessing the Value of Opal
There are certain factors, such as the size, quality, play of color, and the rarity of the stone, that help determine the value of an opal. Important is the intensity of the play of color, as the most valuable gems show a bright play of color even in dim light. In addition to the intensity is the spectrum and pattern of the play of color. Special patterns such as harlequin and pinfire patterns exist in Mexican opal and are highly valued.
Cracking and crazing may significantly reduce the value of a stone. Some types of Mexican opal are unstable so the length of time the stone has been kept is important information to have for anyone trying to find their perfect opal.
A seasoned lapidary person will know what specimens are worth the time to be polished. If opal isn’t stable enough, one might polish it and then it will craze and will be a waste of time. As in any discipline, it is important to know your material first to make a decision on what you’re going to do with it.
The Many Varieties of Mexican Opal
There are several kinds of Mexican opal, with the mexican deposits producing significant amounts of transparent and translucent opal, with warm body colors of yellow to orange-red. These are fire opal, clear crystal opals prized for their base color, which is usually bright orange to orange-red opal and usually faceted with or without play of color. Fire Opal can also display play of color, and this is a rarity called Precious Fire Opal.
There is precious opal, clean and transparent crystal opal, as well as water opal which is also transparent and either the color of clear water with a bluish or golden internal sheen. All mentioned opal are all characterized by having a play of color.
Matrix opal is another kind of Mexican Opal which are sometimes cut in their rhyolitic matrix rock if it has a hardness that will allow for cutting and polishing. Also called cantera opal, these stones were not initially as prized as the pure cuts but cutters and buyers of both koroit/boulder and cantera opal came to appreciate the attractiveness of the matrix cut and polished with the opal.
Magic of the Opal: Play of Color
Fire opal gemstones glow with the fire of the volcanoes that spewed lava where they were produced so long ago: yellows, oranges and reds that are so bright you might think they would glow in the dark! An important deciding factor in the value of the opal is its play of colors, which can include rain or confetti play of colors.
In all types of opals, the play of color depends on the arrangements of the microscopic spheres of opal silica which diffract the light. If the arrangement of these spheres is h
aphazard there is no play of color. Whats produces a play of colors is a regular arrangement of the spheres. The size determines the color. The play of color in Mexican opals is strongly dependent on the intensity of the light in which the stone is viewed. A more valuable s
tone will have a play of color even in dim light, often taking the form of a rolling flash.
Fire opal that displays play-of-color is rare because volcanic opal forms relatively quickly and the spheres of silica rarely have time to settle into the diffraction grids that create play-of-color.
An opal with high translucence and the intense play of colors is highly valued. Different terms for play of color include pinfire, which are small close set patches of color; Harlequin: Broad, angular, close-set
patches of color ; Flame: Sweeping red or reddish flashes of color that shoot across the stone; and rolling flash: Color flashes that appear as the stone is turned. The most valuable fire opals are transparent and red, often called cherry opal because of their bright, bold colors.
Different in appearance are the jelly opal, which is a cloudy or translucent opal, hydrophane, an opaque opal that becomes transparent when soaked in water. Finally there is common or potch opal which has no play of color.
How are Fire Opals Cut?
Most people that mine opals don’t polish them. Mining takes all of your time. It’s a long process when you decide to carve an opal. One has to have to have a lapidary machine, a diamond disc cutter, and also a grinder. Sometimes the grinders are diamond backed wheels. Then you have to have what sands down the opal. In that process, 3 or 4 different sand paper grids need to be used — the final one being really fine sandpaper.
Next you give the opal a luster finish which is basically a leather wheel with water and a powder called sirium oxide. One has to kind of rub the stone with the powdered water and the leather wheel. If kept moist and lubricated, the shine comes out. It is always good to Inspect your work with good light or a magnifying glass.
Fire opals are cut in a variety of ways. Many are cut as faceted stones, so that you get sparkle in addition to vibrant color and the wearer of the gem must be aware of the fragility of the stone. One can facet the opal or make it into a cabochon. Its up to the cutter to decide how the stone will be most attractive.
If It has deep inclusions the opal will be worth a lot more. Sometimes with a rough opal in hand , one might notice little inclusions which are sand — these are minor imperfections that devalue the opal. You can drill the minor imperfection out and polish it irregularly. Carving an unusually shaped stone can greatly increase its value and yield. Carved opal are often called free forms. Cabochons can also be referred to as freeform too, stones that are not cut into a regular shape.
While opal is a highly fashionable stone, it is also dynamic in how it might help a person in other regards. Physically, it is said to have the power to heal the lower back, kidneys, and can stimulate sexual organs. Mentally, the fire opal is a dynamic stone for people who are trying to build self-confidence. Its fire supposedly rouses them and gives them the boost of inspiration they need. Fire opal symbolizes joy of the heart so we can be open to the mystery of life and live in wonder.
Here at Western Opals we’re passionate about having the opportunity to bring people the highest qualities opal and setting fair and decent prices on high quality specimens for long term customers. Tips for buyers; Always buy opal from a reliable source. Ask if the stone has been kept dry, most opal contains 3–10% water—though it can be as high as 20% or more. It is the dry
ing out of the stone’s water content that causes it to craze and crack. If the stone has been dry for 12 months or more it should be stable.
There is something in an opal for everyone, whether you are looking for something fashionable or functional, given the many qualities opal has to offer. Message us today about finding the perfect opal for you.