Ruby is the red variety of the mineral corundum, composed of aluminum oxide. Its distinctive red color comes from trace amounts of chromium. Distinguishing natural rubies from imitations or laboratory-grown versions is important due to differences in their rarity and market value.
Initial Visual Assessment
Observing a ruby’s color provides initial insights into its authenticity. Natural rubies typically display a deep, vibrant red, with the most prized shades often described as “pigeon’s blood” red. This ideal color exhibits a pure red hue without noticeable orange or purple undertones, and a medium to medium-dark tone. Some natural rubies, however, can present with slight purplish or orangy red tones.
Clarity is another visual aspect, and natural rubies are expected to have some internal characteristics, known as inclusions. These can include fine rutile needles, often called “silk,” which are common and can even enhance the stone’s appearance by scattering light. A ruby that appears perfectly flawless to the naked eye should raise suspicion, as such stones are exceedingly rare in nature and are often laboratory-created.
Simple Home Tests
One practical home test relies on the ruby’s exceptional hardness, which is 9 on the Mohs scale. This means a ruby can scratch common materials like glass or quartz, but it cannot be scratched by them. It is important to perform this test on an inconspicuous area of the material being tested, and never on the ruby itself.
Rubies also possess a high density. This property means a real ruby should feel noticeably heavier than a piece of glass of the same size. Another simple observation involves the “cold test,” where a genuine ruby will retain its coolness against the skin for a longer period compared to less dense imitations like glass.
Observing how a ruby interacts with light can offer further clues. Natural rubies often exhibit a red glow or fluorescence when exposed to ultraviolet (UV) light, a phenomenon caused by the chromium within the stone. However, the presence of iron can diminish or even mask this fluorescence, meaning not all natural rubies will fluoresce strongly. Some synthetic rubies can also fluoresce, sometimes with an even more intense glow than their natural counterparts, so this test is not definitive on its own.
Understanding Common Alternatives
Many materials are often misrepresented as rubies, falling into two main categories: natural simulants and synthetic rubies. Natural simulants are different gemstones that visually resemble rubies but have distinct chemical and physical properties. Red garnet, for instance, typically has a darker, more brownish or burgundy tone and a lower Mohs hardness. Spinel, another natural stone, differs in its optical properties. Red tourmaline can also appear similar but often carries purplish hues and is less durable than a ruby.
Synthetic rubies, conversely, are laboratory-grown stones that share the same chemical composition and crystal structure as natural rubies. Their formation in a controlled environment often results in a lack of the natural inclusions found in mined stones. Under magnification, synthetic rubies may display tell-tale signs such as curved growth lines or perfectly round gas bubbles, features not typically present in natural rubies. These lab-created versions offer an affordable alternative but do not possess the same natural origin or market value as their mined counterparts.
When Professional Evaluation is Needed
While home tests can offer initial indicators, they have limitations for definitive identification. Many imitations are visually convincing, and synthetic rubies are chemically identical, making precise differentiation challenging for the untrained eye. For conclusive authentication, consultation with a professional gemologist is recommended.
Gemologists employ advanced testing methods that go beyond simple visual checks. These include microscopic examination of inclusions to identify specific growth patterns or internal features, such as rutile silk in natural stones or gas bubbles in synthetics. They also measure optical properties like refractive index and specific gravity, which can differentiate rubies from simulants. Spectroscopic analysis further helps by identifying light absorption patterns within the stone. Obtaining a gemological certificate from a reputable laboratory is important for valuable rubies, as it provides a certified assessment of the stone’s authenticity, quality, and characteristics.