Flawless Quartz Crystal Sphere at the Smithsonian Natural History Museum (106.75 lbs)
This crystal sphere is the largest cut piece of flawless quartz in the world, weighing in at 242,323 carats! It symbolizes our fascination with something so beautiful and yet so common. Quartz is found around the world, in large quantities, and is considered one of the most common minerals on Earth. It’s found in sand, dirt, and dust. Yet, when fashioned by gem cutters and put in a stunning piece of jewelry, it can be breathtaking.
Quartz is a complicated gemstone. One of the reasons it’s tricky is because the term “quartz” is used for varieties of gems, as well as for a species of gem and as a group of gems. So, for example, Rose Quartz is a variety of the species Quartz. So is Citrine, Amethyst, and Tiger’s Eye! All these varieties, and others that are couched under the species of Chalcedony, such as Agate and Jasper, are considered to be members of the group, Quartz. Very confusing!!
Perhaps it’s best to start with the fact that mineralogists and geologists see any mineral with the chemical makeup of silicon dioxide, SiO2, as Quartz. Regardless of whether the crystals making up that stone are large, small, or microscopic, it’s all Quartz. Gemologists, on the other hand, separate the gems into those whose crystals are larger and those too small to see without a high-powered microscope. Those with larger crystals are called Quartz and those with microcrystalline structures are labeled Chalcedony.
Under these two species are many varieties that are used in jewelry. Probably the most commonly known variety of the quartz species is Amethyst. That regal purple has been admired for centuries. The purple color comes from natural irradiation acting upon a trace element of iron. The saturated, medium to deep reddish purple is the most prized color, but amethyst ranges from a light, pinkish purple to that deep purple hue. Amethyst is not rare, but the prized color is more rare because usually only the tips of the amethyst crystals have that depth of color.
Agate and Amethyst, showing the deep purple tips of the quartz crystals, as well as the microcrystalline Agate, which is part of the Chalcedony species.
Other varieties of the Quartz species include Citrine, the orange-yellow gemstone that’s November’s birthstone, and Rock Crystal, which is colorless because it has no trace elements. There’s also Rose Quartz, Smoky Quartz, Prasiolite (aka Green Amethyst), and Ametrine (a bi-colored gem combining the purple of Amethyst and the yellow of Citrine).
Members the Chalcedony species have been used in jewelry even longer than Amethyst! Agates, which exhibit wavy bands of color, were used in amulets and talismans over 3000 years ago. They were also used to make cameos. Carvers would reveal a differently colored band by carving down around the subject of the piece. Today you’ll see agate slice pendants that are sometimes dyed to accentuate the banding.
Probably the most valuable member of the Chalcedony species is Chrysoprase. This translucent gemstone is beloved for its natural apple-green color. It owes its color to the presence of nickel. A big discovery of Chrysoprase was made in 1965 in Australia. Because its color can resemble fine jadeite, it’s sometimes called “Australian Jade.”
Other varieties of the Chalcedony species include Black Onyx (dyed black chalcedony), Carnelian, Jasper, and Fire Agate. Most chalcedony is translucent to opaque, so it’s rarely faceted. Most often it’s fashioned into beads, slices or cabochons. But, just like all Quartz, it registers a 7 on the Mohs Hardness Scale, making it a good choice for rings and bracelets as well as earrings and pendants.
There’s so much that can be said about this beautiful mineral that surrounds us everyday. But I want to end with the sentiment– “How wonderful when something so common can also be so special!”
Custom-made Ametrine Ring in our showcase!
The romance and history of colored gemstones has always fascinated me. I guess I’m just a sucker for a good story. Here are three I thought you might like.
TANZANITE: It’s said that we are all members of the “Tanzanite generation.” Discovered in 1967 by a Masai tribesman in Northern Tanzania, Tanzanite is mined in only one, 4 square kilometer, location. And the mines are getting deeper and harder to mine profitably. We will be the ones who can buy a new Tanzanite. Future generations will only see the stone in heirloom pieces. It’s estimated that Tanzanite One, the largest Tanzanite mining company, has less than 30 years of production left.
The gemstone was named by Henry Platt, great-grandson of the famous Louis C. Tiffany. Tiffany and Co. realized the importance of the gemstone and quickly made themselves the main distributor. Their marketing efforts made tanzanite one of the most popular gemstones by the 1990s. The beautiful gem hit the big screen with a “splash” as the Heart of the Ocean in the movie, Titanic.
MORGANITE: This pink to orange/pink variety of beryl was originally discovered in Pala, California in the early 1900s. It was named for J.P. Morgan, a great financier and collector of minerals. Tiffany’s gem buyer and gemologist, George Kunz, was the man who named the gem, buying up all he could find for his wealthy client. Incidentally, another pink gemstone, discovered at about the same time, was named Kunzite in honor of George Kunz. So, he got his own gemstone, too!
Morganite is the same species of mineral as Emerald and Aquamarine. Like Aquamarine, it is usually an eye-clean stone that can be cut in larger sizes. It’s a good thing, too, because a larger stone usually shows a more saturated color. Pale Morganite often needs that advantage. It’s generally heat-treated to improve its pink color and minimize its yellowish tint. The treatment is stable, so no fading occurs.
ALEXANDRITE: First discovered in Russia’s Ural Mountains in the early 1830s, Alexandrite is the quintessential color-change gemstone. It was found by miners who thought they’d found emeralds, until nighttime came and they were sitting around the campfire. Alexandrite’s trace elements of iron, titanium, and chromium make it greenish in sunlight and reddish in incandescent or fire light. Boy, were those miners surprised when, the next morning, their red gemstones had turned back to green!
Legend says that the gem was found on the 16th birthday of young Alexander II, future Czar of Russia. The stone became the National Gem of Czarist Russia. It was the perfect fit with the red and green color scheme of imperial Russia’s military. Every Russian had to have an Alexandrite. Unfortunately, for all of us, the Russian supply was depleted. Fortunately, other deposits have been found in Sri Lanka, East Africa, and Brazil.
Natural Alexandrites are very expensive, especially in larger sizes. Even the synthetic version is expensive, because it’s difficult to manufacture. But, if you’re lucky enough to own an Alexandrite, you have an “Emerald by day, and a Ruby by night.”
I’ve lived most of my life in Michigan and my maiden name is Campbell. Most people don’t know that because I’ve been married so long! But I always thought Campbell was a good name, so I was both happy and surprised to learn that there is a gemstone named after. . .no, not me, nor my kinfolk, but after the Campbell shaft of the well known Bisbee Mine in Southern Arizona.
So, what’s the story of Campbellite? As explained by one of the stone cutters at Arizona Lapidary, Campbellite is an uncertain mixture of minerals like cuprite, azurite, malachite, calcite,chrysocolla, pyrite, quartz, and copper. Its color and look varies because there’s no set amount of these minerals. It was first discovered by miners looking for copper. The bosses weren’t interested in this unusual rock, and told the miners to discard it. But the miners had a different plan. They saw its beauty. So, yes, they dumped the Campbellite in the trashcan. But they separated it carefully from the real trash. And when no one was looking, they loaded the discarded gem into the back ends of pickups. Campbellite has been showing up in the market, piece by piece. There’s not a lot of it–I’m sure plenty WAS dumped. The mine closed in 1975, and there is no other known source of Campbellite. But I bought one piece of it, cut into a smooth cabochon, and plan to make a bolo tie for my dad.
I learned a little bit about the mine shaft itself. It was first developed in 1927, originally as a way to get oxygen to other parts of the Bisbee Mine. But soon it was one of the best producers of copper ore, with yields of 8-10% copper.
Finally, who is the Campbell shaft named after? A little research revealed an amazing coincidence. The shaft was named after Gordon R. Campbell, who actually lived and went to school in Michigan! He graduated from U of M in 1893 and was a mining executive and lawyer up in the Keweenaw Peninsula. The Keweenaw Peninsula, jutting from the Upper Peninsula of Michigan, is one of the best known sources of copper world-wide. Towns like Calumet, Houghton, and Copper Harbor were booming back in the mid-1800s because of copper. Anyway, Gordon Campbell helped form the Calumet and Arizona Mining Company in 1901, serving as the company’s President from 1921-1931. It was this company that operated the Bisbee Mine. So Campbellite WAS named for a Campbell living in Michigan. Who knows? Maybe he’s a long, lost cousin?
The Campbell shaft, courtesy of the Arizona Historical Society
Black Opal and Rubellite Tourmaline
I’m married to a man born in October, and I can testify that he’s complicated. But I never thought October’s two birthstones had unusual complexity to them until I started to really study them. Tourmaline has a complex physical nature while Opal has a complex history and symbolic nature. Let’s see if light can be shed on these two amazing gems.
Tourmaline wasn’t recognized as a separate group of minerals until the 1800s. It comes in an unbelievable array of colors, so chrome tourmaline was often mistaken for emerald. Rubellite tourmaline was thought to be ruby. Back in the days before modern mineralogy, gem stones were often identified by their color. Chemically, tourmaline is complicated because many of its elements have the ability to replace one another in a process called isomorphous replacement. That’s why tourmaline from the Paraiba mine in Brazil can be neon blue. Copper is part of its chemical makeup. That’s why chrome tourmaline from Tanzania can be a deep, almost emerald green. Chromium is part of its formula. Pink tourmaline from Zambia has magnesium and black tourmaline (also called schorl) has iron. These gems all have the same basic chemical formula, but it’s a formula that allows for lots of substitutions.
The crystal habit of tourmaline is a unique 3-sided column, with cross sections that resemble rounded triangles. It’s not uncommon to see different colors evident in the same crystal, leading to bi- and tri-colored tourmaline. There’s even watermelon tourmaline which has cross sections that show pink centers and green boundaries. The value of tourmaline is complicated, too. A high quality Paraiba tourmaline sells for tens of thousands of dollars per carat. A large piece of black tourmaline sells on Amazon for under $10.
Paraiba tourmalines photographed from the GIA Collection for the CIBJO project from the Dr. Eduard J. Gubelin Collection.
What’s quite complex about opal is its reputation. It falls in and out of favor, depending on who writes about it, who wears it, and what superstitious stories are made up about it. From ancient mythology, the opal was said to be a symbol of purity, hope, and innocence. It was supposed to be protection against evil. But, during the Black Plague of the 14th century, opal wearers often died. The rumor circulated that it was the opal that caused death. Opals were evil! In the 1500s opinion changed. Shakespeare wrote about opal as the “queen of gems.” It became popular once again. But, in the early 1800s, Sir Walter Scott wrote a book whose character, Lady Hermione, dies soon after a drop of holy water destroys her opal’s colors. It’s uncertain what caused Hermione’s death, but the opal market was clearly dead for 50 years because of Sir Walter Scott’s book.
In 1877, an amazing Australian black opal was discovered, and Queen Victoria decided that she liked opals. Opals were good! She gave one to each of her five daughters, and her love of it made the gem popular again. Today, opals still swim in complexity. Sometimes I’ll hear customers talk about the superstition of opal only being good luck to those born in October. Or they’ll talk about Sir Walter Scott’s book. But my opal has never brought me anything but joy–and I was born in June!
If you’re born in October, be proud of the fact that your birthstones are complicated. It’s much more interesting than perfect clarity! Embrace the mystery.
What’s the difference between carats, karats, carrots, and carets? They all sound the same, but they have very unique meanings. And two of them, carats and karats, are commonly used words in the jewelry industry.
Used to describe the mass of a diamond and other gemstones, a carat is a measure of weight. One carat is equal to 0.2 grams or approximately 0.007 ounces. The name, carat, comes from ancient times when carob beans were used on a balancing scale to measure the weight of light objects like gemstones. A carob bean doesn’t weigh much but, more importantly, carob beans are very consistent in their weight and size. Each one weighs about 0.007 ounces (about the same weight as a paperclip). Another way to think about it is that it takes about 142 beans to make one ounce.
1 carob bean = 1 carat diamond
Historically, weighing light objects wasn’t done consistently. The carob bean was used throughout the Middle East and Europe. Grains of wheat or rice were used elsewhere. And the carat was used to weigh other things besides gemstones. There wasn’t a standard carat weight that was used in all countries. But in 1907, the 4th General Conference on Weights and Measures adopted the “metric carat”, equal to 0.2 grams or 200 mg, as the official and world-wide measurement for diamonds and gemstones.
The term, karat, is usually used to indicate the fineness of a gold alloy. It is a measure of purity. Twenty-four karat gold signifies 100% pure gold. So, using your knowledge of fractions, you can determine that 18 karat gold has 75% gold and 25% other metals. (You can also see my previous blog on metal alloys.). Fourteen karat gold has 58% gold and 42% other metals.
Interestingly enough, the measure, karat, came from the German carat. The Germans had a gold coin, called a “mark”, which weighed exactly 24 carats (4.8 grams). The purity of the gold in the coin was expressed as the number of carats of gold present in the 24-carat coin. Somehow, the letter was changed from “c” to “k” and the karat was born.
So, what about “caret” and “carrot?” Well, a caret is a wedge-shaped symbol indicating the place where something is to be inserted. And a carrot? Well, I’ll let Bugs Bunny explain that one.