GEMMOLOGY

Gemstones: Basic Concepts

"The gems have life in them: their colors speak, say what words fail of." - George Eliot

Gemstones —  natural or artificially created minerals that possess unique properties such as rarity, colour, natural beauty, high hardness and durability. After polishing and cutting, gems exhibit brilliance and play of light, resulting from light refraction and reflection off the stone's facets. Gemstones are used in jewelry, collectioning, and can serve as investment objects.


Some of the key characteristics of precious stones include:

  1. Transparency: Determines how much light passes through the stone, affecting its brilliance and fiery glow.
  2. Clarity: The presence or absence of inclusions and defects, which can influence the appearance and value of the stone.
  3. Color: One of the most important factors, which can vary from vivid and bright shades to more subdued and rare tones.
  4. Cut: The way a stone is shaped, which can significantly impact its optical properties, such as diamond brilliance and brightness.
  5. Hardness: A measure of a stone's resistance to scratches and damage, assessed on the Mohs scale. For example, diamond is the hardest of precious stones.
  6. Rarity: Rare stones, such as Alexandrite or Paraiba tourmaline, are often more valuable due to their uniqueness.

1 carat = 0.2 gramm
Title
Title

Origin of Natural Gemstones

Natural gemstones are stones created by nature without any human intervention. They are found in various places, such as deep underground layers, riverbeds, rocky cliffs, and other natural landscapes.

Some gemstones are formed by powerful natural processes such as tectonic movements, earthquakes, and volcanic eruptions. Others arise from the deposition of mineral-rich waters or the slow burial of ancient forests.

Almost all gemstones are associated with specific types of rocks in the Earth's crust, which fall into three main categories: igneous, sedimentary, and metamorphic.

 

Igneous Origin

When magma, erupted from volcanic vents, slowly cools and solidifies, the concentration of dissolved substances increases, and mineral crystals begin to grow. If this process occurs at great depths, the crystals can grow to significant sizes. On the surface, however, crystals are usually small because the lava solidifies very quickly.

 

Metamorphic Deposits

Metamorphic deposits form as existing rocks are transformed by high temperatures, pressure, and chemical processes. These conditions can convert existing minerals into new, more stable forms, creating a variety of precious stones. For example, limestone can transform into marble, which can contain ruby or sapphire crystals.

Metamorphic processes can also enrich rocks with various elements, helping to form unique precious stones. Garnets, kyanites, and spinels are often found in metamorphic rocks.

 

Placer Deposits and Ancient Forest Burial

Placer deposits are a special type of sedimentary deposit where valuable minerals and gemstones accumulate due to the action of water. As rocks weather and break down, their fragments, including precious stones, are carried by rivers and streams. Heavier minerals such as gold, diamonds, and sapphires settle and concentrate in riverbeds, bends, and natural traps.

 

Thus, the origin of gemstones is a fascinating journey through geological processes. From the deep, slow formation of large crystals in magma, through the weathering and transportation of minerals by natural elements, to the remarkable transformation of ancient forests and metamorphic changes, each stone carries a unique story embedded in its structure.
Title
Title

Synthetic Gemstones

Synthetic gemstones, also known as lab-grown stones, are nearly indistinguishable from natural gemstones in many characteristics. They possess the same crystalline structure, refractive index, density, chemical composition, color, and other properties. The only difference is that synthetic gemstones are created in specialized laboratories.

 

How to distinguish natural gemstones from lab-grown ones? 
Unfortunately, without special equipment, it is impossible. Only gemological laboratories can confidently determine the origin of a stone. Small internal characteristics, such as inclusions and growth defects, help experts identify synthetic gemstones.

Tips for Differentiating Natural Gemstones from Synthetics:

  1. Examine the inclusions: Natural gemstones often contain natural inclusions, such as air bubbles, crystals of other minerals, or fractures, while synthetic stones may be nearly flawless and devoid of such inclusions.
     
  2. Check the color: Some synthetic gemstones have a more saturated and uniform color than their natural counterparts. However, this is not always the case, so color alone is not a definitive indicator.
     
  3. Consider the price: Synthetic gemstones typically cost much less than natural ones, but this is not always the case. Some synthetic stones, especially rare types, may be more expensive than natural stones.
     
  4. Refer to certification: When purchasing a gemstone, consult certified dealers or request an official certificate confirming the stone's origin.
     
  5. Buy from reputable sellers: If you're not experienced in evaluating gemstones, it's best to buy from reputable and reliable sellers who can provide guarantees and certificates for the stone.
Title

Treatment

Treatment is the process by which gemstones are treated to improve their characteristics: color, clarity, and saturation. Most natural gemstones on the market undergo enhancement, making them more attractive to buyers. In nature, it is extremely rare to find gemstones of jewelry quality that are pure, possess rich color, and are free of defects. Naturally, their cost is quite high. Treating other, more affordable stones and transforming them into jewelry-quality specimens allows many people to afford gemstones at reasonable prices.

Methods of Treatment:

Heat Treatment

Heat treatment (for example, of sapphires or tanzanites) is a process in which a gemstone is heated to high temperatures and then gradually cooled. This thermal treatment helps to reduce internal stress within the stone and enhances its color, making it more vivid and saturated. In some cases, it can even completely change the color of the gemstone.

Traditional blow pipe heating in Sri Lanka 

Essentially, heating acts as a catalyst for the natural chemical processes of coloration within the crystal. In other words, the coloring agents that, for various reasons, could not react during the stone's formation get a "second chance." As a result, the gemstone either acquires a more vivid color (as in the case of sapphires, rubies, and tanzanites) or completely changes its hue (for example, smoky quartz becomes colorless). This process can also be referred to as "internal" diffusion because the mixing and reactions occur within the stone itself.
Before heating
After heating

Heat Treatment of Tanzanite
 

The advantages of annealing lie in its relative simplicity and the significant results that can be achieved. Of course, there are always risks of damaging the stone, and traces of such treatment can almost always be detected by a gemological laboratory. It is important to remember that, all other characteristics being equal, a natural, untreated stone is valued much higher.

Diffusion 

Diffusion treatment involves the use of chemicals and heating to change or enhance the color of a gemstone. This method is often used on corundum to either enhance its color or create a star effect.

During the process, the surface of the gemstone (although recently some stones can be colored throughout) is coated with a coloring agent such as titanium, iron, or chromium. Heating then catalyzes the diffusion process, allowing the substance to penetrate the stone. This method of enhancement significantly improves the overall appearance of the gem.

As you can see the coloring agent has been absorbed and changed only in the outer thin part of the stone, while the inner part remains unchanged

It is important to note that diffused stones are valued much lower (sometimes hundreds of times less) than their natural counterparts with the same color. This is not only because any chips, attempts to re-cut, or even re-polish the stone can reveal its colorless or pale core but also because the process of diffusion is seen as a harsh intervention in the natural gemstone. The traces of diffusion are easily identified by specialists, who can provide a corresponding certificate.

Impregnation

Impregnation, involves filling the cracks and cavities in a gemstone with resin, oils, liquid glass, or other polymers. This process is commonly used on porous stones with numerous cracks, for a simple reason: their structure allows them to accept foreign fillers.
 

The technique of enhancement is simple: a liquid composition, often under high pressure, fills the pores and cracks of the stone. As a result of this procedure, the transparency of the cut stone is often significantly improved, which in turn increases its value, and can also intensify the saturation of its color, especially for opaque minerals.

Oil treatment is one of the oldest methods of enhancing precious stones and has a long history of application. Even in ancient times, minerals, including emeralds, were filled with colorless oil to improve their appearance.

Modern methods of oil treatment typically involve the use of natural cedar oil. This oil helps penetrate the cracks of the gemstone, improving its transparency and color. However, it is important to consider that the effect of oil treatment may be temporary, and often requires repeated procedures to maintain the desired appearance of the stone.

It is also important to note that precious stones treated with oil require special care. This is because the oil may seep out of the cracks or be removed upon contact with water, detergents, or other chemical substances. Therefore, owners of such stones are advised to avoid contact with aggressive substances and periodically consult professionals for professional cleaning and treatment renewal.

Irradiation

Irradiation treatment, is a method of treating gemstones that originated from the natural process of radiation exposure in the earth's crust, resulting in a change in their color. Humans have found a way to expedite this process, and now irradiation is one of the main methods of altering the color of gemstones such as topaz, diamonds, and quartz. One of the main advantages of this method is its stability - irradiated gemstones usually retain their color permanently, with rare exceptions when the result may be unstable. For example, the blue and golden color of sapphires obtained through radioactive treatment may sometimes fade over time. This is why radiation is not always applied for enhancing sapphires.

Blue topaz is the most common example of a gemstone treated with irradiation. The color of topaz obtained after irradiation depends on the type of irradiation, its duration, and the heating processes involved. Topaz can have various shades, from sky blue to dark blue with a greenish hue. Rarer color variants include "electric green" and "neon," with shades of green and blue.

Blue Topaz

Is It Safe To Wear Jewelry With Irradiated Gems?

The clear and simple answer is that irradiated gemstones are safe to wear. There have been no reported cases of anyone being harmed by wearing them or any other irradiated gems.

Can a treated gemstone be considered natural?

A natural gemstone is a mineral extracted from the earth. A synthetic stone is a crystal artificially created by humans in a laboratory. For example, a diamond is a natural gemstone, while cubic zirconia is a synthetic analog. Can a natural diamond transform into cubic zirconia during treatment? Absolutely not. This question doesn't require an answer. A treated precious stone remains natural because its structure remains unchanged.
Title

What should I look for when purchasing gemstones?

When purchasing gemstones, the primary aspect to consider is the intensity of color, as it significantly impacts the stone's long-term value.
 

The most desirable color intensity is classified as Vivid, which achieves an ideal balance of color saturation. While more saturated or intense colors can make the gemstone appear darker, thus potentially reducing its value, a faint intensity can alter the gem's appearance completely. For instance, a very light-colored ruby may be perceived as a pink ruby instead.

Unlike diamonds, gemstones do not have a universally accepted color grading system. However, Plamena utilizes seven levels of color intensity:

  1. Dark: Exhibits a moderate to strong saturation with a very dark tone.
  2. Deep: Features a moderate to strong saturation with a medium dark to dark tone.
  3. Vivid: Shows a vivid saturation with a medium to medium dark tone, regarded as the finest balance of tone and saturation.
  4. Intense: Possesses a moderate saturation with a medium light tone.
  5. Medium Intense: Displays a moderate saturation with a light tone.

For sapphires, two additional levels of color intensity are recognized:

  1. Light: Characterized by a slightly greyish or brownish saturation with a light tone.
  2. Very Light: Has a greyish saturation with a very light tone

Carat

The size of a gemstone is primarily determined by its carat weight. One carat is equivalent to 0.2 grams and is often broken down using a point system, where 100 points constitute a single carat. Larger gemstones are rarer and thus more valuable.

Due to this rarity, the price of certain gemstones can increase exponentially with size. For instance, a 10.0-carat ruby may be, on average, a hundred times more expensive than a 1.0-carat ruby.
 

Clarity

The grading system for clarity is quite straightforward, focusing on what is visible to the naked eye without magnification.

In gemstones are common, widely accepted, and often help determine the stone's origin. The three levels of clarity in gemstones are:

  1. Eye Clean (EC1 - EC2): Inclusions are not visible to the unaided eye.
  2. Visible Inclusions (VI1 - VI2): Inclusions are slightly visible to the unaided eye.
  3. Included (I1 - I2): Inclusions are easily noticeable to the unaided eye.

Shape

The shape of a gemstone does not significantly affect its price, as it is primarily a matter of personal preference. The most common shapes:

  1. Round
  2. Oval
  3. Cushion
  4. Pear

Less Conventional Shapes:

  • Rectangle: Octagon, Fancy Octagon, and Baguette
  • Square: Square, Princess, and Asscher
  • Other: Kite, Trilliant, Shield, and Tapered Baguette

Cuts 

Gemstones typically feature a combination of two cuts—the brilliant cut and the step cut—to achieve an optimal balance of vivid color and brilliance. Much like diamonds, the crown of a gemstone is often brilliant cut to enhance radiance, while the pavilion is step cut to intensify color and vibrancy.

 

Emeralds are typically cut into rectangular shapes to ensure greater durability due to their slightly more brittle nature compared to other gemstones.
 

Cost Factors

The final price of a gemstone is influenced by several factors, including color, clarity, origin, treatment, and carat weight. High-quality gems are extremely rare and can see a substantial increase in value.

Before making a purchase, it's advisable to have a clear idea of the quality level you seek. Determine which factors are most important to you and align them with your budget.

Hardness

Mohs scale of hardness

Our Promises

Plamena Jewelry, a renowned jewelry brand, serves as an official dealer and supplier of precious gemstones, offering certificates from reputable independent gemological laboratories. Committed to perfection and quality, Plamena ensures that each precious stone is meticulously evaluated, undergoes quality control, and is certified by trusted experts in the field. When you choose Plamena Jewelry, you can be confident that you are acquiring authentic, high-quality gemstones, backed by authoritative certification, guaranteeing a truly exquisite and reliable investment."

Top 10 Most Popular Gemstones in the World

1. Diamond

1st place is taken by a diamond. 

This gemstone has a benchmark hardness rating of 10. It is one of the most expensive gemstones, yet it does not have the highest indicators that determine its value. This fact is not known to everyone. The brilliance and play of light in a gemstone are determined by its refractive index and dispersion. The higher these values, the brighter the gemstone shines and the more intense the play of light. So, the refractive index of a diamond is 2.4, and the dispersion is 0.044. However, there are gemstones with a higher refractive index than a diamond (hematite 2.9, cinnabar 2.9, proustite 2.8, cuprite 2.8, rutile 2.6), and there are gemstones with a higher dispersion than a diamond as well (cassiterite 0.062, andradite 0.057, cerussite 0.051, sphene 0.051).


Another criterion by which the value of a gemstone is determined is rarity. Diamond is by no means the rarest stone on Earth. There was a case in history when the price of diamonds significantly dropped because the supply exceeded the demand. And after numerous diamond deposits were discovered in Africa, there was a threat of a price collapse in the diamond market, but the situation was rectified by the De Beers company, which artificially created a shortage of diamonds, thereby driving up their price. 

2. Sapphire and Ruby  

2nd place is taken by sapphire and ruby. This is the same mineral - corundum.
 

Corundums are only slightly less durable than diamonds. They are less brilliant than diamonds, and their refractive indices and dispersion are slightly lower.
 

Speaking of sapphire, it is worth noting its rich color palette, but the cornflower blue stone from Kashmir is considered the standard for all sapphires.


Ruby is a red, crimson color. It is surprising that rubies are quite common, but the majority of them are of low quality, and only a few are worthy of use in jewelry making.

The beauty of sapphires and rubies lies in the fact that their color is not affected by the source of illumination (natural or artificial), and they are able to retain their original color without fading for many years.

3. Emerald

3rd place is taken by emerald. 

It is a very delicate and demanding stone that requires special care and handling, as it ranks between 7 and 8 on the Mohs scale. Its brilliance and play of light are lower than that of a diamond and slightly inferior to sapphire and ruby. It is valued for its rich green (grassy) color. Almost all emeralds have numerous micro-cracks, but they do not deter from its beauty; rather, they add uniqueness to the stone. Like ruby, emerald is quite common, but a good emerald is a rarity.

4. Pearls

Pearls are formed from a microscopic grain of sand inside a shell, consisting of layers of nacre that give them incredible luster. While marine pearls are renowned for their value, their freshwater counterparts do not always boast perfect form and are known as Baroque pearls.

5. Topaz

A stone that surprises with its versatility and range of colors: from pure aluminum silicates to crystals with a multitude of shades. Jewelers particularly value its unique, natural tones and remarkable hardness, which almost rivals that of a diamond. This versatile and durable stone combines sophistication with relative affordability.

6. Garnet

Garnet surprises with its variety! Previously, all blood-red gemstones were called "rubies". However, over time, the term "garnet" came to be used only for pyropes and almandines, whose saturated color resembles juicy fruit seeds that gave this stone its name. And although our modern understanding of garnet includes many varieties with different characteristics, it's worth remembering: not all of them have the classic red color.

7. Opals

Opals are valued primarily for their ability to exhibit opalescence - displaying all the colors of the rainbow. This unique property of the mineral is due to the large globules in its structure. During opalescence, the color flashes emanate from within the stone, creating soft and delicate iridescence. However, opals are often counterfeited: in counterfeit items and imitations, the shimmering shades are often observed only on the surface.

8. Moonstone

It is also called adularia. This mesmerizing mineral is especially valued for its mystical rainbow-like glow. The natural palette ranges from delicate milky-blue to sunny-yellow and even black.

9. Tanzanite

One carat is valued from 200 to 2,000 dollars. Primarily, the price is influenced by the color of the stone, which can be blue-violet, violet, blue, or olive. The main feature of tanzanite is its optical effect of trichroism - the ability of the mineral to change color three times depending on the angle from which it is viewed: from olive to blue-violet and then to red-magenta-violet.

10. Tourmaline

One carat of tourmaline can cost from 50 to 500 dollars. Primarily, the price depends on the color of the stone, which can range from pink and green to blue, purple, and even black. However, multicolored tourmalines are most highly valued for their ability to reflect multiple hues simultaneously. Tourmaline is also known for its electrical polarization, making it popular among mineralogy enthusiasts and collectors.

Encyclopedia


LEARN & CONNECT

Join our mailing list!

Be the first to uncover Plamena's exclusive offers and rare gemstone collections! Gain early access to limited-edition pieces!
Thanks for contacting us. We'll get back to you as soon as possible.

About the Shop

Plamena is a jewelry brand designed to fill people with strength using top-quality, natural, certified gemstones and elegant, adjustable-size jewelry crafted by professional jewelry makers on the island of Bali.

info@plamenajewelry.com

More Plamena Jewelry

Encyclopedia

Custom Jewelry

Help

FAQs

Warranty

Returns and Exchanges 

Contact Us

Terms and Policies 

Terms and Conditions

Privacy Policy

Shipping
Title

© 2024 Plamena Jewelry by Los Nuevos Videntes