December Birthstone: Turquoise

Turquoise

18-karat Gold Collar with Turquoise Cabochon

This 18-karat gold collar, designed by Pierre Touraine, is set with a turquoise cabochon of fine texture and color. – Gift of Touraine Family Trust
Turquoise is found in only a few places on earth: dry and barren regions where acidic, copper-rich groundwater seeps downward and reacts with minerals that contain phosphorus and aluminum. The result of this sedimentary process is a porous, semitranslucent to opaque compound of hydrated copper and aluminum phosphate.
Turquoise is a prime example of an opaque colored stone that can be marketed both as a gem for jewelry and as an ornamental material.The Abdurreza Turquoise Mine

The Abdurreza turquoise mine lies in a dry, remote area of Iran.

Turquoise might lack the sparkle and clarity of transparent colored gemstones like ruby, emerald, and sapphire, but its multi-layered history and soul-satisfying color make it a desirable gem. Its color can range from dull greens to grass greens to a bright, medium-toned, sky blue. People value turquoise highly for its combination of ancient heritage and unforgettable color.

The traditional source for the top color, sometimes described as robin’s-egg blue or sky blue, is the Nishapur district of Iran, the country formerly known as Persia. So, quite often, you’ll hear people in the trade call turquoise of this beautiful color “Persian blue,” whether or not it was actually mined in Iran.

Top-quality turquoise has inspired designers to create elegant jewelry. It’s most often cut into cabochons, but it might also be cut into beads or flat pieces for inlays.

Although much turquoise jewelry is sleek and modern, many US consumers are familiar with the traditional jewelry of Native American peoples such as the Pueblo, Hopi, Zuni, and Navajo. People interested in Native American arts and crafts frequently collect this stylized silver jewelry.

Silver and Turquoise Squash Blossom Necklace

Elaborate silver and turquoise squash blossom necklaces like this are prized by collectors of Native American jewelry. – Courtesy Jaime Steelman

Turquoise is relatively soft, so it’s ideal for carving. Artists in Europe, Asia, the Middle East, and the Americas choose turquoise as a medium for carved jewelry and art objects. It’s often fashioned into talismans with Native American significance, such as bird and animal carvings, called fetishes.

Fetishes

Native American jewelry often features carved turquoise birds and animals, called fetishes. Courtesy Jaime Steelman.

Turquoise owes its texture to its structure and composition. It’s an aggregate of microscopic crystals that form a solid mass. If the crystals are packed closely together, the material is less porous, so it has a finer texture. Fine-textured turquoise has an attractive, waxy luster when it’s polished. Turquoise with a less-dense crystal structure has higher porosity and coarser texture, resulting in a dull luster when it’s polished.

Ornate Turquoise Vase

Turquoise is soft enough to be carved. This turquoise from China was crafted into an
ornate vase. – Courtesy Geological Museum, Beijing, China

Porosity and texture don’t just affect appearance: They also affect durability. Turquoise is fairly soft—it ranks 5 to 6 on the Mohs scale. Turquoise with a coarse texture might have poor toughness, too. Samples with finer texture have fair to good toughness.

Van Cleef & Arpels Ballerina Brooch and Matching Clip Earrings

This Van Cleef & Arpels ballerina brooch and matching clip earrings are designed with gold, diamonds, turquoise, and ruby. – © GIA & Tino Hammid, courtesy private collector

In turquoise, low porosity and fine texture are more valuable than high porosity and coarse texture. Coarse, porous stones are usually treated to make them smoother, shinier, and more marketable.

Sky-blue Turquoise

The smooth, waxy luster of these turquoise earrings results from closely grouped crystals that lessen porosity. – Courtesy GLEAM

Turquoise deposits usually form in iron-rich limonite or sandstone. Limonite creates dark brown markings in turquoise, while sandstone creates tan markings. These markings are remnants of the host rock within the turquoise, and can resemble splotches or veins. They’re called matrix.

Turquoise in its Host Rock

Turquoise is generally embedded in its host rock, like this specimen from Iran.

Manufacturers try to fashion turquoise so that no matrix is visible, but sometimes it’s unavoidable. Small amounts of turquoise might be scattered through the host rock in such a way that the rough material can’t yield any cut specimens large enough to fashion into gems without including some matrix.

Matrix in Turquoise

The matrix in spiderweb turquoise is attractively arranged in a network of thin lines.

The presence of matrix can lower the value of turquoise, but that doesn’t mean turquoise with matrix is worthless or unmarketable. Some buyers actually prefer the presence of matrix in fashioned turquoise if its effect is attractive and balanced.

This is especially true if it’s a type of turquoise known in the trade as spiderweb turquoise. It contains matrix in thin, delicate, web-like patterns across the face of the gemstone. The patterns provide a dark contrast to the gem’s bright blue.

In the market for top-quality turquoise, stones with no matrix at all command the highest prices. Gems with attractive spiderweb matrix rank second in value.

Courtesy of GIA  https://www.gia.edu/
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Unique Topaz cuts

imperial topaz

Imperial is one of the most highly prized topaz colors, as seen in this spectacular prize-winning, orangy-red, flame-shaped gem. – Gem courtesy of John Dyer & Co.

TOPAZ RING; 12.25 CT; 1.48 TDW; 39000K; C5217A-001

This ring, designed by Maria Canale, holds a 12.25-carat untreated topaz from Brazil. The gem has no visible inclusions. – Courtesy Richard Krementz Gemstones

Blue Topaz Sculptural Gem (TM) 61.78 cts cut by John Dyer & Co.

This 61.78-carat carved topaz is a truly unique sculptural piece. Skilled workmanship intensifies the blue color to produce an effect like shimmering droplets of water. Blue topaz makes a perfect material for large carvings due to availability in large sizes. Lydia Dyer, Blue Topaz Sculptural Gem courtesy of John Dyer & Co.

November’s birthstone: Topaz

 

london blue topaz

Many consumers know topaz as simply an inexpensive blue gem. They’re surprised to learn that its blue color is hardly ever natural: It’s almost always caused by treatment. They might also be surprised to know that topaz has so many more colors to offer gem lovers, including pinks and purples that rival the finest fancy sapphires. Topaz 3

Topaz is allochromatic, which means that its color is caused by impurity elements or defects in its crystal structure rather than by an element of its basic chemical composition. The element chromium causes natural pink, red, and violet-to-purple colors in topaz. Imperfections at the atomic level in topaz crystal structure can cause yellow, brown, and blue color. Brown is a common topaz color, and the gem is sometimes mistakenly called “smoky quartz.” topaz 2

The color varieties are often identified simply by hue name—blue topaz, pink topaz, and so forth—but there are also a couple of special trade names. Imperial topaz is a medium reddish orange to orange-red. This is one of the gem’s most expensive colors. Sherry topaz—named after the sherry wine—is a yellowish brown or brownish yellow to orange. Stones in this color range are often called precious topaz to help distinguish them from the similarly colored but less expensive citrine and smoky quartz.

Topaz is also pleochroic, meaning that the gem can show different colors in different crystal directions.

topaz range

October birthstone: Opal

"The Path of Enlightenment" Necklace

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.

Black Opal

This black opal exhibits exceptional play-of-color. – Courtesy Cody Opal

The color you see varies with the sizes of the spheres. Spheres that are approximately 0.1 micron (one ten-millionth of a meter) in diameter produce violet. Spheres about 0.2 microns in size produce red.  Sizes in between produce the remaining rainbow colors.

Fine-quality Light Opal

This fine-quality light opal is from Mintabie, South Australia. Almost all of its spectral colors are visible from a variety of viewing angles. – Courtesy Cody Opal

Although experts divide gem opals into many different categories, five of the main types are:

  • White or light opal: Translucent to semitranslucent, 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 bodycolor. 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 semitransparent, with a clear background. This type shows exceptional play-of-color.

Light Opal

This exceptional light opal is from South Australia’s Coober Pedy opal fields. – Courtesy Cody Opal

3.47 Carat Boulder Opal Tablet

The rough specimen is a thin seam of boulder opal on sandstone host rock. The 3.47-carat boulder opal tablet was cut from a similar piece of rough.

September birthstone: Sapphire

Sapphire is a popular gemstone – and comes in a rainbow of colors. It’s also been long prized, from Ancient Greek rulers to the clergy of the Middle Ages. But where does the September birthstone come from?

A Little Bit about Sapphire

Sapphires in a range of colors

Before we embark on our journey to find the September birthstone, let’s start with a little gemological background.

The September birthstone, sapphire, comes in a range of colors: blue, violet, green, yellow, orange, pink, purple and intermediate hues. The gem belongs to the mineral species corundum: corundum is colorless, but trace elements or color centers (small defects in the atomic structure of a mineral that can absorb light and impart color to the stone) can turn colorless corundum into colorful sapphire. Red corundum is the only color not called sapphire; corundum with this color is ruby.

Where Sapphires Come From: Kashmir

3.08 ct unheated Kashmir sapphire

Blue Kashmir sapphire is legendary among gem collectors and jewelry connoisseurs. However, its reputation for gems of unsurpassed beauty rests on stones mined from 1881 to 1887; very little has been produced since then. Sapphire from the mines after this brief window in time varied greatly in quality.

Finding the September birthstone in Kashmir reads like a chapter from an adventure book: we go to northern India, past the picturesque Dal Lake and its famous houseboats, beyond fields of wildflowers and head up into the Himalayas. Our journey takes us on treacherous roads to, as 18th-century explorers described, a “region beyond the snows.” In these remote hillsides, some of the world’s most beautiful sapphires were unearthed.

Srinagar

Fine blue Kashmir sapphire is said to resemble the color of the feathers of a peacock’s neck. Tiny inclusions give gems a velvety appearance. This can look like an extremely fine haze.

A few last facts about Kashmir sapphire: perpetual snow cover makes mining extraordinarily difficult; the mines are exceedingly remote; the weather is severe; and the area is politically contested. Few stones sporadically emerge, and fewer gemologists have researched the mines. That means you’re highly unlikely to find Kashmir sapphire for sale, and if you do, you’ll want a GIA Colored Stone Identification & Origin Report to verify its country of origin. Fine pieces are occasionally sold by leading auction houses.

Blue sapphire

Where Sapphires Come From: Myanmar

rough sapphire crystal

The land north of Mogok, a city in Upper Myanmar. Blue sapphires mined in Mogok tend to have a rich, intense hue; the best of these September birthstones maintain their appearance under all lighting conditions: incandescent, daylight and fluorescent.

Miners outside of Sapphire mine in Mogok

The sapphire mines of Mogok share some similarities with the ones from Kashmir: they are remote, hard to reach and are in a politically-charged land. Sapphires from this locale are also rare; they are found near many of the ruby deposits. Mogok is also famed for producing some of the finest pink sapphires in the world.

oval shape 6.39 ct pink sapphire

Where Sapphires Come From: Sri Lanka

Sri Lanka can poetically be called “Treasure Island”. All colors of sapphire, ruby, cat’s-eye chrysoberyl, spinel, garnet, tourmaline, topaz, quartz and many other gems can be found in the Highland Complex, a wide band that runs roughly down the middle of the island. Some of the finest sapphire is also found here, and in riverbeds scattered across the country.

Miner searching in river gravel

33.16 ct blue sapphire

6.66 ct padparadscha sapphire

Sri Lanka is perhaps the most famous source for padparadscha sapphires; they are found in river gravel throughout the country. Padparadscha means “lotus flower,” in Sinhalese and this name has been given to the pinkish orange to orange-pink variety of corundum. This sapphire’s color has been likened to the color of salmon, sunset and ripe guava. The cause of color for padparadscha sapphire is due to either trace amounts of iron and chromium or color centers. Fine specimens can sell for as much as a ruby.

Sri Lanka is also a source of the September birthstone in many of its colors: green, yellow, pink, purple, and virtually any color in between. Many in the trade consider Sri Lanka to produce the best range of fancy color sapphires in the world.

Where Sapphires Come From: Thailand

Thailand is an important source of sapphire. Gem fields in Chantaburi, in southeastern Thailand, were mined from the late 1800s to the early 1900s. Sapphire now mostly comes from Kanchanaburi (western Thailand), where it is found in rivers and streams. Most sapphire mined in Thailand is heat-treated to improve its color.

Sapphire mines in Kanchanaburi

Thailand is one of the world’s major cutting and treatment centers: sapphire from Myanmar, Cambodia, Australia, Madagascar and Sri Lanka are sent here, and end up in jewelry stores in the United States, Japan and Europe.

Art Deco bracelet

Where Sapphires Come From: Cambodia

On the western side of Cambodia—in the Pailin Province, near the border with Thailand—sapphire rough lies in riverbeds. Miners sift through the gravel, looking for “Pailin sapphire,” which is understood to be fine-quality blue sapphire that is typically water-worn, rounded and hexagonal in shape. Stones are regularly heat-treated to lighten color and remove or reduce inclusions.

Pailin, Cambodia

Mining for sapphire in Pailin is extremely demanding. Deadly malaria and a hot climate are working conditions that require muscle and grit. The Khmer Rouge, an oppressive regime that ruled Cambodia from the 1970s to the 1990s, left a legacy of poverty and landmines that still take lives and limbs. Still, in the midst of these most difficult circumstances, miners search for a piece of rough that can change their fortunes.

Two 11.48 carats blue sapphires

Where Sapphires Come From: Madagascar

Three blue sapphires

Madagascar, an island off the southeastern coast of Africa, is a rich source of gems: garnet, aquamarine, tsavorite, rubies and of course, the September birthstone. Rough sapphire was found in 1993 in the Andranondambo region of southern Madagascar; and in 1998 in IIakaka – a remote, arid land of plains broken by lonely mountains. A new source was found in January 2016 near Andranondambo in an extremely remote and dangerous location. The mine is accessible only by foot, and the area is rife with bandits.

Sapphire mining in Madagascar

Many people rank the color of Madagascar’s blue sapphires between Kashmir and Sri Lanka in quality. Rough is often heat-treated to improve color. Slight inclusions are common, as well as color zoning (bands of color).

Two heat-treated Madagascar sapphires

Madagascar is another source for fancy color sapphire: it produces pinks, blue-violets, yellows, oranges and greens.

Range of different colored sapphires

Where Sapphires Come From: Other Sources

The September birthstone can also be found in other areas of the world. Australia produces blue, yellow and green sapphires. It is primarily a source of commercial-grade sapphire, and occasionally produces high-quality rough suitable for use in fine jewelry. Commercial-grade sapphire is also found in Montana. Tanzania, Malawi and Kenya – countries in East Africa – are other sources of pink, blue-violet, yellow, orange and green sapphires.

Heat treated yellow sapphire (left) and untreated yellow sapphire (right)

18K yellow and rose gold flower pin

 

Courtesy of GIA