Rubies are among the priciest gemstones on the market and hold significant importance in the colored stone industry. Several critical factors are evaluated when grading natural rubies: color, clarity, inclusions, and transparency. Additionally, the cut, weight, and sometimes even the origin, can impact the ruby’s grade.
Based on this grading system, rubies are categorized into different ranks: AAA, AA, A, and B. The chart above illustrates these ranks under each stone.
- Natural AAA – Represents a mere 1% of all natural gemstones, making rubies in this category extremely rare and valuable.
- Natural AA – Accounts for 10% of all natural gemstones globally. Rubies in this grade are of high quality, suitable for fine jewelry.
- Natural A – Comprises the top 20% of natural gemstones. Although not as exceptional as AA, this grade is still highly regarded and used in fine jewelry.
- Natural B – Makes up over 50% of natural gemstones.
Red Ruby Color
The term “ruby” originates from the Latin word “ruber,” meaning red. When assessing ruby color quality, hue, saturation, and tone are key factors. The hue identifies the ruby’s basic color, with ideal hues being red. Saturation determines the color’s purity and intensity, classified as vivid, strong, fair, medium, and weak, with vivid being the highest quality. Tone reflects the color intensity, where a medium tone is considered ideal.
Clarity and Inclusions
Ruby clarity depends on the number and visibility of inclusions. Here are detailed clarity grades for natural rubies:
- VVS – Very, very slightly included. Inclusions are minor and visible only under 10x magnification, not affecting the ruby’s appearance.
- SI1 – Slightly included. Inclusions are large or numerous, noticeable even to the naked eye, with minor impact on appearance and brilliance.
- SI2 – Slightly included, with easy-to-see inclusions under 10x magnification, slightly affecting appearance and brilliance.
- I1 – Obvious inclusions, significantly impacting appearance, brilliance, and transparency.
- I2 – Prominent inclusions, greatly affecting appearance, brilliance, and transparency.
- I3 – Many prominent inclusions, severely detracting from brilliance, appearance, and transparency.
Rubies graded as VVS and VS are considered the highest qualities.
Inclusions, natural characteristics within the stone, vary. Common types in rubies include crystals, needles, silk, cracks, twinning, parting, and halos.
- Crystals – Solid inclusions of varying shapes and sizes.
- Needles – Long, thin inclusions made of crystals or tubes filled with gas or liquid.
- Silk – Fine rutile fibers resembling silk, preferred in rubies.
- Cracks – Feather-like inclusions also known as fractures or fissures.
- Twinning – Two crystals growing from or next to each other.
- Parting – Breakage along a plane of weakness.
- Halos – Circular features surrounding a crystal.
Ruby Transparency
Transparency refers to the degree of visibility through a ruby. This quality is often overlooked. Transparency categories include transparent, semi-transparent, translucent, semi-translucent, and opaque. Transparent rubies offer excellent brilliance despite inclusions. Semi-transparent rubies show objects slightly blurred, while translucent rubies make objects hard to see but allow some light through. Semi-translucent rubies let a small fraction of light pass, and opaque rubies allow almost no light through, with transparent rubies being the ideal and highest quality.
Ruby Treatments
Heat treatment is the most common method used to improve a ruby’s clarity and color. By heating rubies to over 1,700 degrees Celsius, silk can dissolve, enhancing overall clarity and color, thus increasing the ruby’s grade and appeal.
In summary, natural rubies are remarkable gemstones. Their grading considers color, clarity, inclusions, transparency, and treatments, similar to other gemstones.
FAQs
What are the factors that affect the grade of a ruby?
Color is the most important aspect of this gem, and the best quality rubies display a vibrant red to purplish-red hue. Other factors that affect the grade of a ruby include the cut, clarity, and carat weight.
Where does ruby get its name from?
The name ruby is derived from the Latin word “ruber,” which means red.
What are the various types of inclusions found in a ruby?
The various inclusions in rubies include crystals, needles, silk, cracks, and halos.
How is a natural ruby treated?
It is common for natural rubies to undergo heat treatment to improve their clarity and color.
Is an opaque ruby considered good?
No, because almost no light can pass through an opaque ruby, making it look lackluster.
