RUBY

GEMOLOGICAL PROPERTIES OF RUBY

Chemical Composition:

Ruby belongs to the corundum family and is composed of aluminum oxide (Al2O3). The red color is primarily due to the presence of chromium in the crystal lattice.

Color:

The most important factor in evaluating rubies is their color. The ideal color is a vivid, pure red with a slightly bluish hue, often referred to as “pigeon’s blood” red. However, rubies can also range from pinkish-red to purplish-red.

Color Grading:

Gemologists assess the color of rubies based on hue, tone, and saturation. Hue refers to the dominant color, tone is the lightness or darkness of the color, and saturation measures the intensity or vividness.

Cut:

The cut of a ruby affects its brilliance and overall appearance. Common cuts include oval, cushion, round, and emerald cuts. A well-cut ruby reflects light internally and showcases its color.

Clarity:

Rubies often contain natural inclusions, or “silk,” which can affect transparency. Some inclusions are acceptable and can be used to identify the origin of the ruby. However, too many or large inclusions may impact the stone’s value.

Carat Weight:

Larger rubies are rarer and can command higher prices per carat. However, the overall quality of the stone, including color, cut, and clarity, is crucial in determining its value.

Mohs Hardness:

Ruby has a hardness of 9 on the Mohs scale, making it one of the hardest gemstones. This durability makes ruby suitable for various types of jewelry.

Luster:

Ruby exhibits a vitreous (glass-like) luster, providing a brilliant and reflective quality to the gem.

Specific Gravity:

The specific gravity of ruby ranges from 3.97 to 4.05. This property helps gemologists identify and distinguish ruby from other gemstones.

Fluorescence:

Some rubies may exhibit fluorescence when exposed to ultraviolet (UV) light. This property can affect the stone’s appearance but does not necessarily impact its value.

Origin:

The geographic origin of a ruby can influence its value. Rubies from certain locations, such as Burma (Myanmar), are highly prized. Pigeon’s blood red rubies from Burma are particularly sought after.

Heat Treatment:

Heat treatment is a common practice in the ruby industry to improve color and clarity. Many rubies on the market have undergone heat treatment, and it is widely accepted as long as it is disclosed.

Understanding these gemological properties is crucial for gemologists and buyers when evaluating the quality and value of ruby gemstones.