COLORED GEMSTONES

Quality Criteria for Colored Gemstones 

For centuries, colored gemstones have mesmerized us with their extraordinary beauty and vibrant hues. Their ability to reflect light makes them nature’s true masterpieces, perfect for creating exquisite jewelry.

But what truly determines their quality and value?

Color – The Most Important Criterion 

Color is the primary factor in assessing the value of a colored gemstone. Experts evaluate the following aspects:  

✔ Hue – The gemstone’s basic color (e.g., blue, red, green).
 

✔ Tone – The lightness or darkness of the color.
 

✔ Saturation – The intensity and purity of the color.
 

✔ Color Distribution – The evenness of color throughout the stone.
 

✔ Pleochroism – The ability of a gemstone to display different shades when viewed from different angles. 

A gemstone’s color results from various natural factors: 

• Chemical composition and crystal structure – The presence of trace elements influences the hue. 

• Crystal growth irregularities – These can enhance color by filtering certain wavelengths of light. 

The variety of colors is truly remarkable. For instance, tourmaline appears in over 1,000 shades, making precise classification a real challenge. 

The Big Four of Gemstones

Despite the fact that the line between precious and semi-precious stones is no longer so sharp, only four minerals are considered to be of the greatest value and demand in the world. These are the diamond, red ruby, blue sapphire, and green emerald. Although all are gemstones, they differ from each other in color, durability, frequency of occurrence, and places of discovery. In nature, or at gemstone deposits, they are found in their raw state, with irregular shapes and various sizes. In order to be used in jewelry making, they are processed using traditional techniques that include cutting, grinding, and polishing. In addition to these, more modern techniques are also used, such as heat treatment, irradiation, or bleaching.

Diamond
Composed of 100% carbon, the diamond is considered the hardest material on Earth, and can only be scratched by another diamond. The most valuable and in-demand diamonds are completely colorless and chemically pure, but they can also be found in other colors, such as yellow, green, blue, or pink.

Sapphire
Second in hardness only to diamonds, sapphires are known for their velvety blue color, which is due to traces of titanium and iron. Depending on the mineral’s chemical composition, they can also occasionally be found in yellow, orange, or green hues. Popular as ornaments among royal families, sapphires symbolize wisdom, strength, and power.

Ruby
The ruby stands out with its deep red color, which can vary from pinkish to purplish or even brownish tones. Rarer than diamonds and sapphires, rubies are highly sought after as romantic gifts due to their vivid red color, symbolizing love and passion.

Emerald
The softest and thus the most delicate among the “big four.” Emeralds are distinguished by their attractive green color, which can range from light to dark green. In the past, they symbolized life and fertility and were also used as remedies against poison and infections.

Cut and Shape – The Soul of a Gemstone 

The way a gemstone is cut affects not only its brilliance but also how its color is perceived. Master artisans carefully shape each stone to enhance its natural beauty and symmetry. Unlike diamonds, where the cut primarily maximizes brilliance, colored gemstones are cut to optimize color. 

Carat Weight – A Measure of Rarity 

A gemstone’s weight has traditionally been an important indicator of its value. It is measured in carats (ct), with 1 carat equaling 0.2 grams. However, two gemstones of the same weight can have vastly different values depending on their other characteristics. 

Hardness – Strength from Within 

A gemstone’s hardness determines its resistance to scratches and wear. The Mohs hardness scale ranks minerals from 1 to 10: 

• Corundum (rubies and sapphires) has a rating of 9, making it the hardest among colored gemstones. 

• Diamond is the hardest natural substance on Earth, with a rating of 10. 

Clarity – A Measure of Transparency 

A gemstone’s transparency directly influences its brilliance and value. Inclusions, which form naturally during the gem’s creation, are often considered flaws but can sometimes add uniqueness and desirability. 

• Star sapphires and rubies – Microscopic needle-like inclusions create a star effect, making them highly sought after. 

• Emeralds – Inclusions known as “jardin” (French for “garden”) are often seen as part of their unique identity and do not necessarily diminish their value. 

Colored gemstones are more than just adornments – they are nature’s artworks, shaped by time and external elements and influences. Understanding the criteria that determine their quality ensures that each gemstone you choose is not only captivating but also genuine, rare, and truly special.