From the enduring allure of rubies and mesmerising hues of emeralds to the sparkling clarity of diamonds and tourmalines - natural gemstones have long been treasured for their timeless appeal. But what should you keep in mind before purchasing one? And how do you evaluate the quality of your gemstone? Read our guide to help you navigate the enchanting world of natural gemstones.
Formed over millions of years by the combination of minerals under immense pressure and heat, colored stones are a true marvel of nature and have long been treasured for their unrelenting scintillation. Gemstones are commonly used in jewelry across the world. Not only that, most cultures associate gemstones with the different months of the year to be worn as birthstones. But what sets one colored stone apart from others, and what determines its quality and value? What should you keep in mind before purchasing a gemstone for jewelry or as a birthstone? We delve into these questions and more, to help you navigate the enchanting world of colored stones with confidence, and make an informed purchasing decision.
The 4Cs: Colour, Clarity, Cut, & Carat Weight
By looking beyond the enrapturing appearance of a colored stone and examining any subtle inclusions or growth features trapped within its crystals, gemmologists can determine the stone's geographic origin and authenticity, and appraise its value. This is where the mnemonic 4Cs of gemstones – Colour, Clarity, Cut, and Carat weight - come in handy. The 4Cs of gemstones is a globally used framework to determine a gemstone’s quality and value.
The 4Cs mnemonic was coined in the 1940s by the Gemological Institute of America (GIA), a non-profit organisation and the leading global authority on diamonds, coloured stones, and pearls. They were further developed into a now universally utilised GIA D-to-Z Colour Scale and GIA Clarity Scale for diamonds. Today, the 4Cs are a globally recognised method for assessing the quality of gemstones and are used universally by experts, sellers, and buyers.
1. The Colour
The colour is the first thing you notice when you see a gemstone. It is what helps you distinguish between them right at the first glance. So it is only logical that colour is the first consideration in the 4Cs of gemstones. To the uninitiated, rubies may be red, emeralds green, sapphires blue, and diamonds colourless, but to the practised eye of a gemologist, each colour has three aspects: hue, saturation, and tone. The hue is the overall shade of colour, such as red, blue, or green, while the tone is the relative lightness or darkness of the hue, and its saturation is the intensity of the hue. Generally, the highest-valued coloured gemstones are those with uniform and deep hues, with intensely saturated colours.
The Ideal Colour of a Gemstone
Although coloured stones occur in a plethora of hues depending on their type, origin, and structure, some colours are preferred to others and are therefore more valuable. Sapphires, for example, occur in several hues - the most popular being blue and yellow. The most valued blue sapphires are royal blue and cornflower blue with medium to medium-dark tones. In yellow sapphires, the finest specimens are bright yellow and deep fluorescent yellow with vivid saturation. Rubies, ideally, are pure and vivid red (also called Pigeon’s Blood in the trade) and those with overtones of orange, pink, and purple are less valued. The most desirable emeralds usually have pure deep green hues that are intensely saturated. Diamonds are usually colourless, but coloured varieties such as yellow, purple, pink, and orange also exist. Such coloured diamonds are extremely rare in nature, are highly sought-after, and command a premium value.
2. The Clarity
Clarity is another aspect of the 4Cs of gemstones that influences the value of a gemstone. It indicates the relative transparency of the gemstone caused by the presence or absence of inclusions (materials trapped inside the gem), fractures, and blemishes that affect its appearance, structural integrity and overall scintillation.
Gemstones are formed deep within the Earth’s crust over millions of years. During this period, changes in heat and pressure can create a multitude of variations in rough gem minerals – where minuscule materials and impurities inevitably enter their crystals. As such, most natural gemstones have inclusions and blemishes of some kind - those with a high degree of clarity are rare and are a chance encounter that can cost a fortune.
Inclusions & Blemishes: Defects or Character?
Sometimes, during the formation of a gemstone, materials inevitably get trapped within its crystal structure. These trapped materials can be traces of other minerals, gases or other fluids, and are called inclusions. The clarity of a gemstone is determined by the size, number, and visibility of such inclusions and blemishes. Gemstones with few or no visible inclusions or blemishes are of higher clarity and are generally more valuable because of their scarcity in nature. Depending on how they affect the gemstone’s structure, inclusions can be of several types, with the most common ones including:
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Color Bands & Color Zoning: These are uneven colouring in a gemstone caused by changing conditions during its formation, rather than by something being trapped within.
Figure 1: A Sphalerite with distinct colour bands (Source: Gem Sphalerite)
Figure 2: This Emerald shows strong colour zoning effects when viewed from the bottom (left) as against the top (right) (Source: GIA) -
Feathers: A feather is a crack or a break in the gemstone - named after its whitish or translucent appearance that looks like feathers trapped within the gemstone.
Figure 3: A Feather inclusion in a diamond (Source: Dupuis Blog) -
Fingerprints: These are networks of tiny tube-like structures often filled with fluids, that resemble fingerprints, commonly seen in sapphires and rubies.
Figure 4: Fingerprint inclusion in a Sapphire (Source: Pinterest) -
Silk/Rutile inclusions: Rutiles are among the most distinctive inclusions in gemstones – often called ‘Silk’ in the trade. These are networks of a needle-like mineral called Rutile, that appear in the form of a mesh or lattice within the gemstone, and have a look similar to that of silky textiles.
Figure 5: Rutile needles or "Silk" within a Blue Sapphire (Source: GIA)In addition to inclusions that are part of the internal structure of a mineral, gemstones can also have blemishes, which are external frailties on the surface of a gemstone, such as scratches, chips, cracks, or abrasions.
Figure 6: A smoky Quartz with cracks (Source: Shutterstock)
Inclusions and blemishes can affect the way light travels through a gemstone and may reduce its overall transparency and clarity. As such, depending on their type, size, and location with respect to the overall structure of the gemstone, inclusions can be treated to reduce their effect on the overall scintillation of the gemstone. Most blemishes too, can be removed by cutting or polishing. Read more about these enhancements in our section on gemstone treatments.
It is important to note, however, that some gemstones with visible inclusions or blemishes can still be of high quality and value, depending on the overall quality of the gemstone and the specific type and location of the inclusion or blemish. Inclusions like silk, when present in the right location, can even enhance the scintillation of the gemstone. Many buyers even consider inclusions as a character of the gemstone and seek these unique stones for their rarity and aesthetic value.
While most gem testing laboratories don’t perform a complete analysis on gemstone inclusions, reports on inclusions can be obtained from gem testing labs like the Gemological Institute of America (GIA), International Gemological Institute (IGI), and Gemmological Institute of India (GII), among others. To know more about which gem testing labs provide detailed gemstone analysis, reports, and certificates, read our gemstone authenticity & certifications guide.
Inclusions & Integrity
At times, small inclusions like cavities and feathers may not significantly affect the gemstone’s clarity but may compromise the structural integrity of the stone. They can cause gemstones to crack and break under relatively light impact. Knowing whether a defect is significant will take the trained eye of a gemmologist. Highly accurate results can be obtained after testing in gemology labs. This underlines the need to always choose a gemstone seller that you trust and certified gemstone laboratories.
3. The Cut
A gemstone or a diamond in its uncut form is far less recognisable relative to its scintillating finished form. Uncut gemstones can even be mistaken for ordinary crystals, for example, uncut diamonds, which are sometimes mistaken for clear quartz crystals. The cut of a gemstone refers to the way it is shaped and faceted, and it can have a significant impact on the gemstone's scintillation (sparkle) and brilliance (light reflection). Expert lapidaries perform cutting to achieve the best aesthetic form of the gemstone while least affecting its weight. Gemstone cutting can be done in two ways - a gemstone can be faceted or cut en-cabochon. Both have their unique appearance and characteristics.
Faceted gemstones have numerous flat surfaces or facets. Faceting involves cutting gemstones to enhance their brilliance and sparkle. Faceted stones, such as diamonds, sapphires, rubies, and emeralds, are prized for their ability to refract light and create dazzling displays of colour. In contrast, cabochon-cut gemstones are shaped into smooth, rounded domes with a polished surface. Unlike faceted gemstones, cabochons lack facets, allowing their natural colour and internal patterns to shine. Cabochon cutting is common for opaque or translucent stones like turquoise, opal, and moonstone, as well as certain transparent varieties like garnet and amethyst.
Identifying a Well-Cut Gemstone
A sculpture is a work of art carved from an otherwise unimpressive rock. The same logic follows for gemstones. Faceting affects the ability of a gemstone to reflect light and create sparkle. The size and shape of the facets, as well as their placement and symmetry, can affect a gemstone’s scintillation and brilliance. A well-cut gemstone will usually have even, symmetrical facets that reflect light evenly and create a sparkling and dazzling appearance. Gemstones cut en-cabochon are expertly shaped and polished for a smooth, rounded dome with a flat bottom. Their surface is free from scratches, chips, or other blemishes, and the dome is symmetrically shaped. On the other hand, poorly cut gemstones can have uneven, blemished surfaces or asymmetrical facets resulting in a dull and lifeless appearance.
Spotting a Poorly-Cut Gemstone
Identifying a well-cut gemstone is quite difficult for non-professionals. Detailed gemstone testing requires equipment usually only found in gemology labs. Nevertheless, there are basic examinations that you can conduct to understand if a gemstone is well-faceted.
First, a magnified look at a gemstone using an eyeglass or loupe can help one understand if the piece has any major issues. The facets, which are the surfaces that reflect light, should be smooth and free of pits, scratches, and dull areas. The edges of the facets should be distinct and crisp, rather than rounded.
You can also check for windowing, which is a result of poor-quality faceting, and happens when the gemstone’s bottom facets are cut at a shallow angle that does not reflect light properly. Such gemstones lack scintillation and look good only in the well-lit conditions of an exhibit. They cannot enhance the look of any jewelry pieces they are studded into. Another way to evaluate your gemstone is to compare its looks with a similar-sized gemstone and see how the light interacts and reflects in both.
Figure 7: Window Effect on Spinels from worst-cut (left) to the best (right) (Source: GIA)
4. The Carat Weight
The carat weight is perhaps the most well-known feature of the 4Cs of gemstones. It refers to the weight of the gemstone and is equal to 0.20 grams. Another unit commonly used in India is the Ratti, which equals approximately 0.91 carats or 0.18 grams. You can click here to use our versatile Carat Converter.
Gemstones with a higher carat weight are rarer and are much harder to find than those with a lower carat weight, and because of their scarcity, they are coveted by collectors and buyers for jewellery. As such, a gemstone’s value and price increase exponentially with heavier carat weights, and lapidaries need to find the perfect balance since faceting the stone to increase its scintillation inadvertently reduces its carat weight. This perfect balance between appearance and carat weight is unique for each gemstone.
Choosing Your Ideal Gemstone
The colour, clarity, cut, and carat weight - all have a significant part to play in determining the value of a gemstone, but these features need to be considered in unison, rather than in isolation. The importance of each feature depends on the priorities of the buyer - some may appreciate a clear and transparent gemstone, whereas others may place greater importance on its colour saturation or cutting. The 4Cs also determine how a gemstone looks when used in jewellery. Large birthstones, when worn in a ring, may suit someone of a large stature but look peculiar on a petite individual. A gemstone with a deep saturated colour may not go well with a subtle metal like silver or platinum.
In addition to the 4Cs, which is a great basic framework for enthusiasts and buyers, the geographic origin is a significant consideration for coloured stones as well. An heirloom sapphire from a region that has stopped producing the gemstone, is worth much more than gemstones from an abundant source or an inferior-quality mine. For example, both Burma and Africa have ruby mines, but Burmese rubies are known for their superior quality and rarity compared to African rubies, which are more abundant in nature and are usually highly treated. Another instance is Kashmir blue sapphires, which are valued more than blue sapphires from Sri Lanka (Ceylon), for their superior colour saturations and exceedingly limited supply. While Kashmir’s mines were depleted long ago, blue sapphires continue to be found in Sri Lanka.
While scarcity can be a factor in determining the value of a gemstone, it does not necessarily mean it is of higher quality. It may be necessary to make compromises and choose a gem that fits within your budget and suits your personality. When shopping for gemstones, remember that there is no such thing as a “perfect” gemstone – but at Precious Earth, there certainly is one that is perfect for you. Ultimately, the most important factor to consider when purchasing a gem or piece of jewellery is the joy and satisfaction it will bring you.
Frequently Asked Questions (FAQs)
Which Natural Gemstones Can I Buy Online in India?
You will find most gemstones that you can buy offline to be also available online. At Precious Earth, we deal in precious gemstones like diamonds, sapphires, rubies, emeralds, and pearls. We also deal in semi-precious stones like agate, citrines, zircon, opal, amethyst, moonstone, and aquamarine.
Do the 4Cs of Gemstones Apply to Both Precious & Semi-Precious Stones?
Though traditionally associated with diamonds, the 4Cs of gemstones can be applied to virtually all coloured gemstones to evaluate their value. The colour, cut, clarity, and carat weight are fundamental criteria for assessing gem quality, and can be applied to semi-precious stones like citrines, garnet, zircon, agate, topaz, aquamarine, and spinel. The standards for each attribute will vary depending on the type of gemstone.
How Can I Make Sure the Gemstones I Purchase Online Are Real and of Good Quality?
Unless you are a professional gemmologist, it is difficult to ascertain the authenticity and quality of a gemstone. So make sure the gemstone comes with a certificate of authenticity when making a purchase. Ensure that it discloses all the essential details of the gemstone, such as its physical and chemical characteristics, and details of treatment, if any.
At Precious Earth, quality has been our priority for over 85 years. We ensure complete transparency by providing certified gemstones with accompanying certificates of authenticity. Additionally, we offer detailed reports from renowned gem testing laboratories like GIA, IGI, GII, and more, upon request. What's more, our commitment to your satisfaction extends with our lifetime returns policy, guaranteeing a genuine purchase every time.
Are There Any Specific Care Instructions for the Gemstones I Purchase Online?
Whether you are purchasing diamonds, rubies, sapphires, emeralds, or semi-precious stones like garnet, tourmaline, amethyst, aquamarine, quartz, topaz, or peridot, gemstones purchased online are no different than gemstones purchased offline. When purchasing online, make sure that you buy from a trusted seller that is reputable and has credible reviews. Gemstones, whether they are purchased online or offline, need to be handled with care. To know more about gemstone treatments and how to handle treated gemstones, read our complete gemstone care guide.
