The October birthstone, opal, is noted for its individuality, magic, and mystery. Its unique display of flashing rainbow colors is unlike any other gem, and has been compared to volcanoes, galaxies, and fireworks.

Throughout history, its intense visual qualities have made it a source of supernatural beliefs.  Bedouins believed that opals contained lightning and fell from the sky during thunderstorms. Ancient Greeks believed opals guarded them from disease. They’ve even been attributed with the power to preserve blond hair!

An opal’s value is determined in part by its background  color. A darker base with vivid flashes of color is the most desirable, and opals with dark gray to black base color are the most valuable. One famous black opal is the 700 carat stone Napoleon gave his wife and Empress Josephine de Meauharnais called “The Burning of Troy” because of its red flashes against a black  background color.  A more  affordable type of  opal has a white  to medium gray background color, called white opal.

Black opals, like this 29.85 carat gemstone from Australia, are prized for their rarity and fiery color. Courtesy of Mariora, Surfers Paradise, Australia

Another key factor in determining an this gemstone’s value is the amount and distribution of flashing rainbow colors, called play-of-color. Play-of-color occurs because of the interaction of light with its internal structure. This causes light waves to diffract, or bend, resulting in spectral colors that range from , red, orange, yellow, green, and blue. There are two broad classes of opal: precious and common. Precious opal displays play-of-color, common opal does not.

“The Path of Enlightenment” necklace contains 180 opals, and is an excellent example of the vast spectrum of colors found in opals. Courtesy of Impressions Ltd.

These gemstones are some times treated to improve their color. Synthetic opal, created in the 1970’s is available in black, white, and fire opal. You may also run across imitation opals made out of glass (called Slocum Stone) and plastic.

If you’re the fortunate owner of a precious opal, the best way to care for it is with warm, soapy water. Ultrasonic cleaning or steam cleaning are never recommended for this fairly delicate gemstone. With a hardness of 5-6.5 on the Mohs scale, it is softer than many gems and should be treated with care.

Opal salamander pin (bottom). (C) GIA and Tino Hammid. Courtesy of Neil Lane, Inc.; Beverly Hills, California.

How would you describe the play-of-color found in opals–flashing rainbow, volcano, galaxy, fireworks? Use your imagination to come up with a way to describe this unique phenomenon.

The post Opal: The gemstone with fire inside appeared first on GIA 4Cs Blog.

Think of every passing year as an opportunity to celebrate with your birthstone. In fact, people have been wearing birthstone jewelry since the 15^th century in Poland, when they were encouraged to own all 12. And while birthstone secrets and lore can be found right here on our blog, today we share what makes YOUR birthstone a powerful statement of your finest qualities.

The post Discover the Powers of Your Birthstone appeared first on GIA 4Cs Blog.

Dazzling gemstones lit the red carpet at this year’s 85th Academy Awards on Sunday, February 24^th. Striking gowns enhanced by colored gems topped our list of favorite styles. Bold shades of blue, like those worn by Robin Roberts and Lilly Collins, were flawlessly paired with brilliant blue sapphire jewelry. Here are some interesting facts about sapphires and other blue gems provided by our GIA experts that every colored gemstone lover should know.

Actress Lily Collins wearing an array of beautiful diamond and sapphire jewelry.

Fun fact: The name “sapphire” can apply to corundum of any color (and there are many besides blue, including yellow and pink), as long as it’s not red, which would then likely be qualified as ruby, another corundum variety.

Sapphire

When the trace elements of the mineral species corundum are iron and titanium, the corundum is blue sapphire. It can be a pure blue, but ranges from greenish blue to violet blue.  Only a few hundredths of a percent of iron and titanium can affect the color, and the more iron the corundum contains, the darker the blue.

Russell Shor, GIA’s senior industry analyst, says that blue gems are a constantly evolving trend: “While sapphire will always be popular, high-quality blue sapphire is scarce in the market right now, so tanzanite has regained much of its past popularity for consumers tapping into the trend of vibrant blue gems. In addition, favorably-priced stones such as blue topaz have become in vogue.”

Tanzanite

Fun Fact: Tanzanite is mined commercially only in one area of the world: the Merelani Hills of Tanzania, where it gets its name.

Another magnificent blue gemstone option boasting bold shades of blue is Tanzanite. This gemstone is the blue to violet-purple variety of the mineral zoisite. Its appearance is influenced greatly by its pleochroism, which is the ability of a gemstone to show different colors when viewed in different crystal directions. Tanzanite can be violet blue—similar to a sapphire color—or much more purple. Often, both the violet blue and purplish colors are readily visible in a fashioned stone when it is gently rocked and tilted.

Blue Topaz

Fun fact: Since the 1970s, treatments have brought blue topaz to a broad market.

Blue topaz is an additional blue gemstone alternative. In nature, topaz is most commonly colorless, and naturally strong blue gems are extremely rare. In the marketplace, however, strong blue shades are plentiful because they have been treated with a combination of radiation and heat to produce blue hues in topaz.

Opals and Emeralds

While blue jewels complemented the Oscars’ stunning couture, several A -listers donning blue gowns opted for other spectacular colored gemstone choices. Jenna Deway-Tatum and Jennifer Hudson wore blue gowns completed by white and black opals, which exhibited a magical blue iridescence. Black opals are rare and considered the most valuable opal variation. Learn more about opals.

Isla Fisher in David Webb carved emeralds and diamond drop earrings.

Isla Fisher was stunning in Emerald earrings, which created a striking contract with her deep blue gown. For more information about Emeralds, check out our post ‘How to Wear and Identify Emeralds’.

Which one of these Oscar gemstone looks was your favorite? Please join us tomorrow for the next segment of our two-part series on Oscar jewels!

The post Colored Gems at the Oscars: Part 1 appeared first on GIA 4Cs Blog.

As passions ignite this month, a jewelry gift featuring a red gemstone is a token of love that can be enjoyed every day. While seen mostly in fashion jewelry, red gemstones are showing up as an option for the primary stone in engagement rings. Celebrities like Jessica Simpson, who sports a 5-carat ruby engagement ring, have been influential in bringing gemstones to the forefront of bridal trends. In addition to rubies, garnets and red diamonds, which we discussed yesterday, the following gemstones are more options for those looking to celebrate this Valentine’s Day with a gift of a spectacular red gem.

Tourmaline
Tourmaline comes in more colors than any other gemstone, but Rubellite is the trade name for tourmaline in the pink to red color range. Rubellites are widely available and come in larger sizes making them a favorite choice for contemporary jewelry. Tourmaline has a hardness of 7 to 7.5, so they are durable enough for daily wear.

Red Spinel
Often confused for rubies, red spinel is a brilliant gemstone sought after for its hardness and intensity of color. Spinel is an uncommon gemstone that is surprisingly affordable. Many famous “rubies” in royal jewel collections around the world are actually spinels. With a hardness of 8 on the Mohs scale, spinel is a durable choice for daily wear.

Opal
Opals are usually known for their iridescent “play-of-color” but occasionally you’ll find the unique shifting of color in a fire opal. The top color for fire opal is usually red-orange to bright red, . Opals are a softer gemstone with a hardness of 5 to 6.5, so special care should be taken.

Based on the selection of gemstones above, which red gemstone would you most like to gift this February?

The post Red Gemstone Buying Guide – Part 2 appeared first on GIA 4Cs Blog.

Opal, October’s birthstone, is a captivating gemstone because of its unique optical characteristics. Opals often exhibit a spectrum of colors called “play-of-color,” which is when viewed from various directions. The Roman naturalist, Pliny the Elder, referred to opal’s play-of-color in the 1st century AD when he wrote: “For in them you shall see the living fire of ruby, the glorious purple of the amethyst, the sea-green of the emerald, all glittering together in an incredible mixture of light.”

This 67.81-carat carved opal from Brazil looks to be glowing from within.

When set against a dark background, the stone is known as “black opal” and is considered rare and very valuable. The more commonly found “white opal” has a light background. Australia produces 95 percent of the world’s fine opal.

The “Sandia Sunset” brooch/pendant has a spectacular 6.18-carat opal from Lightning Ridge, Australia surrounded by garnets, red spinel, Sri Lanka sapphire and eight round diamonds. Gift of Paula Crevoshay

Treasured in the Middle Ages, the opal was called ophthalmios, or eye stone, due to a widespread belief that it was beneficial to eyesight. Some even thought the opal’s effect on sight could render the wearer invisible. Today, October’s birthstone represents hope.

Valued for its shifting play of color, opal’s rainbow hues offer the colors of all the other gems combined.

Check out opal in the GIA Celebrates Birthstones exhibit at the GIA Carlsbad campus. Schedule a free tour 24 hours in advance by contacting guestservices@gia.edu; calling 800-421-7250, ext. 4116 or 760-603-4116; or visiting www.gia.edu.

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October babies have the pleasure of enjoying two birthstones to commemorate their birthdays – tourmaline and opal. Last time we wrote about pink tourmaline, and now we’re going to share with you about opal.

Opal’s name originated in ancient Rome where it was called “opalus” which was synonymous with “precious stone”. Opals are valued for their unique shifting colors in rainbow hues – a phenomenon gemologists call “play of color”.  What causes this?

Play-of-color occurs because opal is made up of sub-microscopic spheres stacked in a grid-like pattern, like layers of ping-pong balls in a box.  This structure breaks up light into spectral colors.  The colors you see depend on the sizes of the spheres.  Those approximately 0.1 micron (one ten-millionth of a meter) in diameter produce violet.  Spheres that are about 0.2 microns in size produce red.  Those in between produce intermediate hues.

The ancient Greeks believed opals gave their owners the gift of prophesy and guarded them from disease.  And throughout most of history opal has been regarded as the luckiest and most magical of all gems because it can show all colors.  Once, it was thought to have the power to preserve the life and color of blonde hair (!).

Opals are more commonly mined in Australia, but are also found in Mexico,  Brazil, Ethiopia and other countries Although experts divide gem opals into many different categories, the main types are:

• White opal – translucent to semi-translucent with play-of-color against a white or light gray body color.
• Black opal – translucent to opaque with play-of-color against a black or other dark body color. The market supply of this type is extremely limited, and so it is considered the most valuable.
• Fire Opal – transparent to translucent with brown, yellow, orange, or red body color.  This material, which often does not show play-of-color, is also known as “Mexican opal,” “gold opal,” or “sun opal.”

Pieces of white or black opal that are too thin to use alone often become part of opal doublets or triplets.  In these assembled stones, a sliver of opal is cemented, usually with black adhesive that dramatizes the play-of-color, to a backing such as chalcedony, glass, or plastic.  A doublet consists of two pieces (the opal and the backing), while a triplet also has a protective top made of rock crystal quartz or colorless glass.

Opals are a 6 on Mohs scale of hardness and are softer than other gemstones so should be worn and stored carefully to prevent scratching and protect them from hard blows. Opals are generally stable to light, but heat from intense light can cause fracturing (known as crazing). They should not be exposed to  acids or caustic alkalis and loss of moisture and crazing can result from storage in airtight containers, such as safe deposit boxes. How do you clean an opal? Easy – use warm soapy water (made with mild dish soap) and a soft bristled toothbrush . But no ultrasonic or steam cleaning, please.

Do you own an opal or want to buy an opal for an October birthday gift or special moment? Find the GIA gemstone buying guide here: Gemstone Buying Guide.

The post All About Birthstones: Opal for October appeared first on GIA 4Cs Blog.