Magazine 58F

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October 18, 2024

Under the Opal Lights

History and beliefs surrounding opal

The word Opal comes from from the Sanskrit word “upala"meaning"precious stone”, passing through Greek "opallios" which would designate the color changes.

Opal has a rich history: many authors have compared it to volcanoes, galaxies or even fireworks.

The Romans considered it the most precious of gems because opal is the only stone that has all the colors,
The Greeks believed that opal gave its wearer gifts of prophecy and immunity to disease,
While Europeans have long considered it a symbol of happiness, hope, purity and truth, this beautiful reputation was shaken by the influence of a 19th century novel written by the Scotsman Walter Scott, who accused a princess of being demonic. When she wears an opal on her forehead, the gem loses all its colors and the princess is upset... before disappearing, leaving behind only a handful of ashes. For those who read the novel to the end, it appears that the opal was protective and the princess poisoned, but alas the image of the opal will remain in France as a stone of bad luck until the 20th century.

Properties of opal

The term opal refers to a family of minerals composed of silica and water with inclusions of various elements.

Each opal is unique. Unlike other minerals, its crystals do not have a particular shape; it is called amorphous gem since it does not have a crystal system. Lapidaries cut it into a cabochon in order to preserve its play of light, but it can also be faceted.

It is important to know that opal contains 3 to 30% water, and can therefore dehydrate over time, which can cause cracks and reduce its iridescence. Setting can also dehydrate opal due to heat, pressure and shock and it should not be subjected to ultrasound. Opal is also sensitive to soap, cosmetics and cleaning products, so it is best to remove your opal jewelry when applying these products.

Finally, the density of opals varies from 1.98 to 2.50 and their hardness on the Mohs scale is 5.5 to 6.5. You must therefore be careful of friction, especially if it adorns a ring.

The different types of opals

There are 2 types of opals:

Noble opals, highly sought after in jewelry, exhibit an iridescence phenomenon, that is, they show a play of sparkles reminiscent of a rainbow. These optical effects are produced by the diffraction of light on silica nanospherules (cristobalite) arranged in a cubic stack held by a siliceous gel and form a network causing light interference when the gem is exposed to light.

Common opals, on the other hand, contain heterogeneous or irregular nanospherules, and therefore have a single color (for example fire opals).

White opal: translucent or semi-translucent, with a white or clear background with multiple effects. It is one of the stones best known to the general public.
Black opal: opal with a dark gray, dark blue, dark green, or gray-black background; deep black (exceptional) which is why we sometimes distinguish between black opal and dark opal. Black opal is rarer than white opal.
Fire Opal: transparent or semi-transparent, orange-red in color, which sometimes has only one color, also known as Mexican opal.
Opal matrix: Opal inclusion forming streaks or pockets within the parent rock.
Opal pebble or boulder: translucent or opaque, black or dark in color with a play of colors and of great solidity. It comes in the form of a pebble whose interior is said to have been filled with opal.
Harlequin Opal: transparent to translucent, it is composed of multiple segmented colored shards. It is one of the most prized opals
Water opal: noble blue-grey opal with rare play of colours
Crystal opal: red reflections on a colorless vitreous background
Sunflower opal: transparent, almost colorless, with a luminous blueish reflection

Origins

Mining opals is not an easy undertaking. It requires geological expertise, mining skills and, of course, patience. Opal occurs in very dry regions of the world, but it There are two types of extraction:

Sedimentary, from Australia

During rains, water carries fine silica spheres by leaching, which accumulate on layers of sandy clay. Little by little, these silica spheres organize themselves and assemble together during a period of drought. This then forms the opal (in its raw state) that we know.

To extract Australian opals, there is surface mining: miners use open-pit mining techniques such as dredging or washing, the aim being to recover opals from gravel and sand deposits. However, they do not have precise scientific clues to guide their search and rely on their instincts. This is why they can spend several months before unearthing precious stones.

Australian opal mines are the most famous and productive in the world, representing a significant part of the country's economy. They are located mainly in the southern regions of Australia such as Coober Pedy, Lightning Ridge and Andamooka.

Volcanic rocks from Ethiopia

Opals from Ethiopia also called "Welo Opals"because they come from the province of Welo, located in the northern part of the African continent.

Since their discovery in the early 1990s, this region has become an important source of opals. Unlike many other opals that form in sedimentary environments, Welo opals are primarily sourced from volcanic environments, particularly in nodules and veins in basalt.

The opalization process occurs when silica-rich water seeps into the cavities and cracks of volcanic rock. Over time, the silica detaches from the water and forms layers of hydrated silica gel. As these layers solidify and compact, they form the opal material.

In the past, opals came from Egypt, India or Saudi Arabia. Today, it is Australia and Ethiopia that produce them. 90% of opals sold in the world. But they are also found in Brazil, the United States, Guatemala, Honduras, Indonesia, Japan, Mali, Mexico, New Zealand, Peru and Russia.

Opal Symbolism

Opal is the birthstone of those born in October, and is given to celebrate the opal wedding, which denotes the 21st wedding anniversary.

Historically, the Greeks considered opal to be a bearer of hope and a symbol of purity. It was said to increase clairvoyance, make meditation and reflection easier, and improve intuition. In India, it represented the Trinity (Trimûrti) composed of the creator god Brahma, the preserver god Vishnu and the destroyer god Shiva.

In lithotherapy, opal would calm and soothe, promote love and tenderness, improve the sentimental life of Gemini and Aquarius. It would open the mind to spiritual life and restore vitality to tired people.