Rubies are among the most valuable and sought-after gemstones in the world. Their deep, vibrant red color has captivated humanity for thousands of years, and they remain the ultimate symbol of passion, power, and luxury. But with such high value comes the challenge of identification. How can you tell a genuine, natural ruby from a synthetic one or an imitation? This comprehensive guide will teach you the professional techniques used to identify natural rubies with confidence.
Before we dive into identification methods, it's important to understand what a ruby actually is. Ruby is the red variety of the mineral corundum, with chromium being the element responsible for its red color. Blue sapphire is also corundum, but colored by iron and titanium. The presence of chromium is what makes rubies so special — and so valuable.
Natural rubies, especially those from Myanmar (Burma) and Sri Lanka, have unique characteristics that help gemologists identify them. Understanding these characteristics is the first step in ruby identification.
Natural rubies typically display a deep, rich red with slight purple or pink undertones. The finest color is often called "pigeon's blood red," a term originally used to describe the best rubies from Burma. This color is vivid, slightly fluorescent, and appears to glow from within. Rubies that are too dark (brownish-red) or too light (pinkish-red) are less valuable.
One of the most distinctive features of natural rubies is their fluorescence. Under long-wave ultraviolet light (UV), many natural rubies will glow a vivid red or pink. This fluorescence is caused by the chromium content and is often used as a quick screening test. However, not all natural rubies fluoresce, and some synthetic rubies may also glow, so this test should not be used alone.
Natural rubies have characteristic inclusions that help identify them. These inclusions are often referred to as the stone's "fingerprint." Common inclusions in natural rubies include:
Professional gemologists use a combination of tests to identify natural rubies. Here are the most important ones:
Natural ruby has a refractive index of 1.762-1.770. This means that a ruby will have a specific reading when placed on a refractometer. Synthetic rubies have the same RI, so this test doesn't differentiate between natural and synthetic, but it does help distinguish ruby from imitations like red spinel (RI 1.718) or red glass (RI 1.5-1.6).
Ruby has a specific gravity of 4.00-4.05. This means it is relatively heavy for its size. Synthetic ruby has the same SG, so again, this test helps rule out imitations. Red spinel, for example, has an SG of 3.60, while red glass has an SG of about 2.5.
Ruby is doubly refractive, meaning it will rotate light in different directions. This property can be seen using a polariscope. Synthetic rubies (especially those grown by the Verneuil method) may appear singly refractive due to their internal structure.
This is one of the most important tools for ruby identification. A jeweler's loupe or gemological microscope allows you to see the inclusions that are characteristic of natural ruby. Look for:
Place the ruby under a long-wave UV light. Natural rubies often glow a vivid red or pink. This fluorescence can sometimes help differentiate natural from synthetic, as some synthetic rubies glow too strongly or in the wrong color.
Identifying synthetic rubies is one of the biggest challenges for gemologists. Synthetic rubies have the same chemical composition and physical properties as natural rubies, making them difficult to distinguish with standard tests. However, there are some clues that can help:
It is important to understand that most natural rubies are treated to improve their color and clarity. Knowing about these treatments will help you make an informed purchase:
If you don't have access to gemological equipment, there are still some tests you can do to get a general idea about a ruby's authenticity:
Identifying natural rubies requires knowledge, experience, and the right equipment. While this guide provides a solid foundation, there is no substitute for professional gemological training. If you are considering buying a ruby, always work with a reputable dealer and ask for a certificate from a recognized laboratory. A ruby is a significant investment, and taking the time to verify its authenticity is always worthwhile.