May, my favourite month, because it’s my birth month, but also we get to talk about the most revered, green gemstone. Emerald is known to be the traditional birthstone for May and is the rich, vivid green variety of the mineral beryl that symbolizes the rebirth and renewal that comes with spring. Emeralds have a long history, with known records of mining dating back to 1500 BCE in Egypt. This was the primary source of emeralds for many years until the 1600’s when the Spanish invaded South America and discovered the source in Colombia. Today Colombia is still the primary source of emeralds with 50-95% of the world’s emerald production. Zambia is in second place and while emeralds are rare, they can be found worldwide. Even Canada is host to several small deposits of emerald in the Yukon.
Just like aquamarine, Emerald is identified as:
- 1) Hexagon Crystal System, not to be confused with crystal habit. (Note, habit is how the mineral crystallizes)
- 2) Silicate Composition, – Cyclosilicate Sub-class
- 3) Silicate Family
- 4) Mineral = Beryl – Be3Al2Si6O18
- 5) Variety = Emerald.
As stated before, the varieties of beryl aside from emeralds that you may know well are aquamarine (see March’s blog post for more), morganite (light pink/peach), and heliodor (golden yellow). However, there are other kinds as well such as goshenite (colourless), red beryl (deep red/crimson), green beryl (light lime to mint green) and mixixe (deep blue colour but fades to brown in daylight due to UV).
How is emerald so green? Emerald, (derived from σμάραγδος or smaragdos; ancient greek for “green gem”, big surprise there) gets its colour from traces of chromium, vanadium and iron within the crystal structure. If you want a real head-scratcher, chromium is also responsible for the red colour of rubies. Interestingly this all comes down to how light interacts with chromium ions, chromium(III) to be specific, within the crystal lattice. Without getting too technical, when chromium is in the beryl it will absorb more of the violet and yellow-red wavelengths of visible light, thus we see green. With rubies, the chromium absorbs more of the blue-green and some yellow wavelengths and thus we see red. Vanadium on the other hand just gives you green and if iron is present, it can give the emerald a blue tinge.
Ready for some REAL gemmology? With the high price of emeralds, there are many synthetics and imitations to watch out for when hunting for emeralds. First, some terminology needs to be explained, mainly the terms “natural”, “synthetic”, “imitation” and “treatment”. A natural gemstone refers to a stone made from the earth and is what most people desire/expect. A synthetic gemstone is an identical copy of a natural, just made by man. This means it has the same chemical formula and crystal structure as its natural counterpart. Ideally, the term “synthetic” should only be used if the man-made stone has a natural counterpart. If there is no counterpart, then this stone is referred to as an “imitation”. An imitation is a stone or material representing another stone. Imitations can be natural or synthetic and confuse many people. Cubic zirconia is one of the most common samples for imitating precious stones. Treatment or a treated stone is a natural stone that has been tampered by humans to improve colour saturation, clarity, and durability. There are many interesting ways we have discovered to help improve the natural beauty of precious stones.
For emeralds, the most common treatment you will see is oiling, due to their clouded and brittle nature. Oiling is as the name suggests, the stone is placed in heated oil in a vacuum chamber and the oil is then drawn into the cracks of the stone. This helps increase the colour in pale stones and seal up fractures to improve the stone’s clarity and durability. Balsam and cedar oil are what is used for emerald treatment as the refractive index of the oils is similar to the refractive index of emerald, thus you can hide the fractures better. This is a common treatment with emeralds and is not always disclosed in the sale. Avoid using strong dish soap and ultrasonic washers if you want to wash your emerald jewellery.
Luckily for you, emeralds are highly desired that we even accept the impurities within them. This will include fractures, pockets, and other mineral inclusions. You will hear many refer to the impurities as the emeralds jardin; the garden within. With these impurities present, it is fairly easy to discern if you have a natural or not, as synthetic and imitation emeralds will appear internally flawless. A flawless gem is the most prized gem. Many of these features of the jardin can be seen with the naked eye or with a loupe. When it comes to synthetic stones, you’ll need a microscope to discern the origin of your emerald as you won’t have a jardin. If there is something in your synthetic stone you’ll know right away something is off. All gemstones leave clues as to how they formed within the crystal structure and carry trace element signatures. While the chemical signature is the best way to identify a stone’s origin you have to destroy a piece of your stone. I don’t think many people would be interested in having a hole in their $25,000 emerald to see if it’s natural or synthetic. Thus by using high powered microscopes and polarized light, gemmologists can see signatures as to how gemstones crystallized and your stone is left untouched. Synthetic emeralds are produced either through the flux method or hydrothermal method. These methods should be disclosed when selling synthetic/lab-created emeralds and if not, ask.
If you’re buying emeralds or you’re not sure if the ones you have are natural emeralds, you’re best to seek professional help with a certified gemmologist to identify them or buy them for you. Otherwise, here are several tips to keep in mind if you happen to find yourself in the market to buy one.
First, most “emerald” you find will actually be imitations. Look at the name of the product. Always question something if you see anything attached to the name aside from “natural”. Many stone dealers will sell items with “emerald” in the title to make the stone more alluring. Under section § 23.26 of the Federal Trade Commission’s Summary of Basis and Purpose for the Revised Jewelry Guides, it states that “It is unfair or deceptive to mark or describe an industry product with the incorrect varietal name”. Titles like “emerald tourmaline”, “emerald quartz” or “yellow emerald” and “emerald colour” should raise suspicion right away. Another example is if there is a name in front other than a location, “Soude emerald” is one example of emerald coloured glass, a common cheap imitation. After looking at the name, look at the price. Emeralds are not cheap and if you think you’re getting an amazing deal for a clean stone with vivid colour, it’s probably not a real emerald. Even synthetic emeralds are more costly than natural imitations like tourmaline, diopside and dyed quartz. Third, if you are buying emeralds in jewellery, check the metal and surrounding stones if there are some. It’s not worth it to set an emerald in plated metal and with cubic zirconias, you end up greatly devaluing your emerald that way. Finally, if you are buying rough emeralds in bulk or individual specimens check your stones and always buy from a well-reviewed source. Look for a hexagonal prism shape or something to give you an indication of 6-fold symmetry in your crystals.
While these are just some quick pointers for general interest if you are interested in more information I suggest some of the links and books below.
- Well-rounded information regarding the formation of emeralds, grading of emeralds and identifying synthetic or imitation stones with some deeper technical insight.
- GIA encyclopedia page for emeralds. Very friendly for just starting to understand gemstones with links to countless articles about emerald mines, unique specimens, emerald history and more
- Gemmology by Peter read – A gemmologist bible, make sure to look for the latest addition as there is always new information to be added to textbooks. This book covers ALL the gemstones as well as how to use the tools to identify naturals, synthetics and imitations. Warning this book is very technical.
- Jewels: a secret history by Victoria Finlay – an excellent read into the history and lore behind some of the more renowned gemstones. The author also has a great book about the history of pigment and colour.
Stay tuned for next month as we discuss pearls… or moonstone or alexandrite. One of those stones or June.