Gems according to your astro
Collecting gemstones is a remarkably rewarding endeavor. Everybody collects for different reasons, but we love that Mother Nature has seen fit to spread her beautiful, natural jewels all across the globe. Starting a collection allows us all to own something tangible and alluring from all four corners of our incredible planet.
The science of gemstones is called gemology, and you could spend the rest of your life researching just one gem and still not know everything there is to know about it. Every gemstone has a fascinating and unique history, from its formation millions of years ago to its journey from the mine to your home. We’re always aware that new customers are joining us and starting their jewellery and gemstone collections, so we wanted to put together a beginner’s guide for anyone taking their first steps into the fascinating world of gemstones, which we’re delighted to present to you here.
WHAT IS A GEMSTONE?
To be classed as a gemstone requires that three essential criteria are met. Each stone must be beautiful, durable and rare.
Let’s explore what this means.
As the saying goes, beauty is in the eye of the beholder, so this point is somewhat subjective. Any rock that is transparent with a strong body colour will unquestionably be considered a gemstone, but there’s so much more to gems than the very cleanest and clearest stones.
If a gem is going to spend a lifetime on your hand or in your ears, it’s going to need a bit of strength. Gemstone durability is generally measured by its hardness, using a system known as the Mohs scale, which was created by the German geologist Friedrich Mohs in 1812. In simple terms, each gem is given a score between 1 and 10, with 1 being the softest (defined as Talc) and 10 being the hardest (defined as Diamond). Mohs created his scale based on which gemstones would scratch the others on his list. Nothing but another Diamond will scratch a Diamond, which is why it heads the table. Ruby and Sapphire score a 9, so they will scratch everything else on the list, including each other, but not a Diamond. If you’re going to wear your jewellery every day, it’s best to stick to the stones higher up in the table. This is precisely why Diamonds, Rubies, Sapphires and Emeralds are considered such good stones for everyday wear, and why they are so closely associated with engagement rings. These are the defining minerals for each of the 10 levels of the scale:
- Corundum (Ruby & Sapphire)
- Quartz (Amethyst & Citrine)
There are entire encyclopedias on the formation of individual gemstones – the process is fascinating, incredibly technical and involves more variables than we could ever list. What follows is a very simplified explanation of how some gems form.
Like a recipe for a meal, each gemstone is made up of a list of ingredients – in the case of jewels, these are elements from the periodic table. If you take Quartz as an example, it is made up of silicon and oxygen, and its formula is written as SiO2, which is also called silicon dioxide. So silicon and oxygen need to be present for Quartz to form. But Quartz in this state is not a gemstone. In fact, Quartz is the second most abundant mineral on Earth, so it definitely isn’t ticking the rarity box we discussed earlier. However, if you add in just the right amount of iron, the perfect amount of heat and an almost incomprehensible amount of time, what you’ll have is Amethyst – definitely a gemstone. If the heat is a little higher, it will result in Citrine, or tweak the iron content slightly and you’ll find Prasiolite instead. They’re all types of Quartz, but they’re all different colours and are beautiful, durable (7 on the Mohs scale) and very rare.
Take carbon. The chemical formula for this is C. Graphite and Diamond are both forms of carbon with the same chemical formula, but they look very different. The variants that make a Diamond what it is are extreme heat, tremendous pressure, and millions of years. Most, but not all gemstones feature a crystal system too – a recognised pattern in which the gemstone’s atoms bond. Diamonds form in a cubic crystal system, giving them a natural shape that looks like two four-sided pyramids stuck together at the base. As an aside, this is why the playing card shape is called Diamond too – it’s no coincidence, they’re the same thing. The requisite pressure for Diamond comes from the fact they formed around 100 miles underground. Similarly, gemstones are often found in areas that have seen significant tectonic activity, such as mountain ranges where two tectonic plates have collided over millions of years.
Similarly, the gemstones Kyanite, Andalusite and Sillimanite all share a chemical formula of Al2SiO5 but have different colours, crystal systems and even hardnesses that are all dependent on the exact pressure and temperature they formed at. We could go on, but for the sake of brevity, we’ll add that the formation of gemstones is essentially a huge coincidence, a meeting of absolutely perfect conditions stretched over a very great length of time. It’s not hyperbolic to call them miracles – they are.
Most gemstones were discovered purely by accident. We can safely assume that the earliest gems to be discovered would most likely have been found just lying on the ground, or in streams. As mentioned, many gems form in mountainous regions and natural erosion over a long period has washed away the rocks from these hidden deposits and carried the gemstones downstream, where they have been deposited on riverbanks and in the streambeds. Pearls and Amber were likely washed up on beaches and discovered lying on the sand. Once we knew they existed, the digging and diving began!
Some of the more recent gemstone finds come with detailed accounts of the moment they were unearthed, such as with Tanzanite or Ethiopian Opal. But many of the world’s most celebrated stones were discovered such a long time ago that their origin stories are sadly lost to time. We can only speculate what the Ancient Egyptians made of the first Turquoise pieces, or what the Ancient Aztecs said when they first set eyes on Fire Opal. Gemstone mining itself is an old trade – Lapis Lazuli is thought to have first been mined in Afghanistan around 12,000 years ago.
Sometimes gemstones are found when mining for other minerals or precious metals. Csarite®? was first found in Turkey in a working bauxite mine. Diamonds form deep in the Earth, but Peridot is also found around 100 miles underground. The deepest we’ve ever dug into the Earth is around seven-and-a-half miles, so how do we even have these two stones? Volcanic activity over the millennia has pushed the deep rocks closer to the surface. These once magmatic shafts are known as kimberlite pipes, and this is what Diamond prospectors look for. If they find Peridot, they know they’re on the right track.
There are generally three ways that gemstones are mined, although of course the size and scale of the mining operation varies significantly from mine to mine. There are substantial commercial mines with modern equipment and a large workforce right down to small artisanal miners, sometimes with as little as a single miner digging through their small claim with hand tools. Mines are found all over the world in many different countries, and certain countries are renowned for the quality of the stones they produce. Examples of this include Colombian Emerald, Sri Lankan Sapphire and Australian Opal.
Perhaps the most immediately recognisable form of mining is this method, where a vertical shaft is dug to a certain depth, and then horizontal tunnels are dug out from this central point like the spokes on a bicycle wheel. This requires the prospectors to find a ‘seam’ of gemstones, which is a layer of gem-rich material sandwiched between other layers of Earth. These seams rarely run in straight lines or stay at a uniform depth, so once one is found the job of the miners is to track the seam as it winds through the Earth underground. Seams only extend so far and will eventually run dry, and then the race is on to find another seam. This can lead to remarkably complex underground warrens of tunnels.
This method is very much a ’leave no stone unturned’ approach – literally! The mine is dug as a giant hole on the surface, so the entire pit is open to the skies, and every last piece of soil is checked for gemstones. This is often done in giant sieve-like devices that wash the dirt away until just rocks remain, which are then all manually checked by eye. Once a certain viable depth is reached, these mines often start to move across the land, filling in the hole behind them and replanting trees as they go. There have even been cases where the disturbed land has been later used to create new farmland. This method is excellent in very gem rich sites but is rather an expensive way of mining if the gemstone yield is an unknown quantity.
This is the name given to gemstones that are found in rivers and streams, including in old dried-out lake beds and stream beds. While the water may not be flowing anymore, the areas beneath the surface where it once did can harbour a trove of gemstones. It’s not unknown for prospectors to still pan for gems in running streams too.
Once gemstones have been retrieved from the ground, they need to be cut or polished before they can be set into jewellery. Opaque gemstones such as Turquoise and Agate tend to be polished into a cabochon (dome) shape. Transparent and most translucent gems tend to be cut, or ‘faceted’ to use the technical term, which involves placing a very specific pattern of flat surfaces or ‘facets’ onto the rough gem. While this has a certain intricate beauty all of its own, the actual reason this is done is to improve the way light enters the gem, is bounced around inside the gem and is then shone back out of the gem. The most known and popular cut is called the Round Brilliant Cut, which is made up of 58 facets and was perfected from centuries of trial and error by a gentleman named Marcel Tolkowsky in 1919.
If you think back to the natural shape of a Diamond, our two back-to-back four-sided pyramids, and then cut off the top third, you are left with the basic silhouette of a modern round cut. People realised a long time ago that letting more light into the top of the gem improved the colour and brightness of a gemstone, and over the centuries this was refined until Tolkowsky perfected the methodology behind the cut. It is still the basis for the Round Brilliant Cut to this day. There are many other cuts too, such as the Antique Cushion Cut and the Marquise Cut to name but two. We also welcome gemstone artists to our studios to share their own cuts, often perfected over many years, such as the QuasarCut by Glenn Lehrer and the Snowflake Cut by Rudi and Ralph Wobito. Innovative new gemstone cuts are referred to as ‘Fancy Cut’.
Faceting a gemstone improves its fire, lustre and brilliance. Fire is the splitting of white light into its constituent rainbow of colours and is famous in Diamonds, and also present in many other stones, including Sphene and Zircon. Lustre is the surface reflection of the exterior of the gem, the light that is bouncing off the stone without entering it. Brilliance is the return of light to the eye from within the gem. These three types of light interaction are what we might informally refer to as ‘sparkle’. A lapidarist does the faceting work on a cutting wheel. It takes many years to learn this art to a proficient level, and these skills are often passed down family lines. The technology that drives these cutting wheels may have improved, but the incredible skills are ancient.