What is an Opal?
Opal is the product of seasonal rains that drenched dry ground in regions such as Australia’s semi-desert “outback.” The showers soaked deep into ancient underground rock, carrying dissolved silica (a compound of silicon and oxygen) downward.
During dry periods, much of the water evaporated, leaving solid deposits of silica in the cracks and between the layers of underground sedimentary rock. The silica deposits formed opal.
How Opal Forms
Opal is known for its unique display of flashing rainbow colors called play-of-color. There are two broad classes of opal: precious and common. Precious opal displays play-of-color, common opal does not.
Play-of-color occurs in precious opal because it’s made up of sub-microscopic spheres stacked in a grid-like pattern—like layers of Ping-Pong balls in a box. As the lightwaves travel between the spheres, the waves diffract, or bend. As they bend, they break up into the colors of the rainbow, called spectral colors. Play-of-color is the result.
Although experts divide gem opals into many different categories, five of the main types are:
White or light opal: Translucent to semi translucent, with play-of-color against a white or light gray background color, called bodycolor.
Black opal: Translucent to opaque, with play-of-color against a black or other dark background.
Fire opal: Transparent to translucent, with brown, yellow, orange, or red body color. This material—which often doesn’t show play-of-color—is also known as “Mexican opal.”
Boulder opal: Translucent to opaque, with play-of-color against a light to dark background. Fragments of the surrounding rock, called matrix, become part of the finished gem.
Crystal or water opal: Transparent to semi transparent, with a clear background. This type shows exceptional play-of-color.
Opal’s Physical and Spiritual Healing Properties
Writers have compared opals to volcanoes, galaxies, and fireworks. Admirers gave extraordinary opals poetic names like Pandora, Light of the World, and Empress. In ancient Rome, this gem symbolized love and hope. The Romans gave it a name—opalus—that was synonymous with “precious stone.”
Many cultures have credited opal with supernatural origins and powers. Arabic legends say it falls from the heavens in flashes of lightning. The ancient Greeks believed opals gave their owners the gift of prophecy and guarded them from disease. Europeans have long considered the gem a symbol of hope, purity, and truth.
Caring for your Opal
Opal hardness is variable depending on its exact composition and formation conditions, and ranges from 5 to 6.5 on the Mohs scale. Its toughness is very poor to fair, making opal a gem that is suitable for jewelry but requires care when wearing so as to not scratch or break the stone.
Opal is generally stable, but heat from intense light can cause fracture lines called “crazing.” High heat or sudden temperature changes can also cause opal to fracture. Opal is attacked by hydrofluoric acid and caustic alkaline solutions.
Opals can be treated by impregnation with oil, wax, or plastic, and by surface modifications called sugar treatment and smoke treatment.
The only safe way to clean opal is with warm, soapy water.
What is a Tourmaline?
Tourmalines come in a wide variety of exciting colors. In fact, tourmaline has one of the widest color ranges of any gem species, occurring in various shades of virtually every hue.
A tourmaline’s chemical composition directly influences its physical properties and is responsible for its color. Tourmalines make up a group of closely related mineral species that share the same crystal structure but have different chemical and physical properties. They share the elements silicon, aluminum, and boron, but contain a complex mixture of other elements such as sodium, lithium, calcium, magnesium, manganese, iron, chromium, vanadium, fluorine, and sometimes copper.
Tourmaline’s Physical and Spiritual Healing Properties
One of the earliest reports of tourmaline in California was in 1892. In the late 1800s, tourmaline became known as an American gem through the efforts of Tiffany gemologist George F. Kunz. He wrote about the tourmaline deposits of Maine and California, and praised the stones they produced.
Basic talents the tourmaline possesses (regardless of its color) includes promoting inspiration and happiness, reducing fear, and building self-confidence. It also balances yin-yang energies. Helps bridge physical with the spiritual.
How to care for your Tourmaline
Hardness and toughness
Tourmaline ranks 7 to 7.5 on the Mohs scale. Its toughness is considered Fair.
Tourmaline is generally stable to light and isn’t affected by exposure to chemicals, but heat can damage a tourmaline. High heat can alter the color, and sudden temperature change (thermal shock) can cause fracturing.
Some tourmalines might have been treated to improve their color. The two most important tourmaline treatments are heating and irradiation.
The best way to clean Tourmaline is with warm, soapy water.