The allure of uncut rubies lies in their raw, unrefined beauty. However, this very rawness makes discerning their authenticity a complex task. While cut rubies have faceted surfaces that can reveal certain tell – tale signs more clearly, uncut rubies present a rugged exterior that demands a more in – depth examination.
Color and Crystal Structure
Color
Genuine uncut rubies typically exhibit a rich, deep red color, though the shade can vary from a vivid “pigeon – blood red” – the most prized hue – to a slightly pinkish or purplish red. The color should not appear too uniform or overly bright, as if it were neon – like. The red color in real rubies is due to trace amounts of chromium within the crystal lattice. If the color seems artificial, too intense without any natural variation, or has a yellowish undertone, it could be a sign of a fake.
Crystal Structure
Rubies belong to the corundum mineral family and have a hexagonal crystal structure. In their uncut state, you might be able to spot signs of this hexagonal shape, although it may be incomplete or distorted. They often form in metamorphic rocks like marble or igneous rocks such as basalt. If the uncut stone shows parts of its host rock still attached, and the overall shape and growth patterns suggest a natural origin within these rock types, it increases the likelihood of it being a real ruby. However, nature is not always uniform, and rubies can also be found as water – worn pebbles, especially in places like Sri Lanka, where identifying the crystal structure becomes more difficult.
Scratch Test, Density Test, and UV Light Test
Scratch Test
Rubies are extremely hard, scoring 9 on the Mohs scale of mineral hardness. This means they are highly resistant to scratching. You can perform a simple scratch test using a piece of quartz (which has a Mohs hardness of 7) or a sapphire (also a type of corundum with a hardness of 9). Gently try to scratch the uncut ruby with the quartz or sapphire. If the ruby is genuine, it should not be easily scratched by the quartz, and it should be able to scratch a softer material like glass. However, be cautious when conducting this test, as it can potentially damage the gem or the testing material.
Density Test
The density of a ruby is relatively high, around 4.00 (±0.05) g/cm³. You can conduct a density test at home with some basic materials. First, weigh the uncut ruby using a precision scale to get its mass in grams. Then, fill a graduated cylinder with a known volume of water, for example, 50 ml. Carefully lower the ruby into the water using a thin string or tweezers. The water level will rise, and the difference in the water volume before and after adding the ruby gives you the volume of the ruby in cubic centimeters. Calculate the density by dividing the mass by the volume. If the calculated density is close to the expected density of a ruby, it is likely genuine. Keep in mind that this method requires precision, and small errors in measurement can affect the accuracy of the result.
UV Light Test
Some rubies exhibit fluorescence under ultraviolet (UV) light. Place the uncut ruby under a UV light source, which can be a simple black – light bulb. Natural rubies may fluoresce red or orange – red under long – wave UV light, while some may show a weaker or no fluorescence under short – wave UV light. However, not all real rubies will fluoresce, and some synthetic or treated rubies may also show fluorescence. So, this test should be used in conjunction with other identification methods.
Common Fakes in the Market
Synthetic Rubies
Synthetic rubies are made in laboratories and have the same chemical composition as natural rubies but lack the natural inclusions and growth patterns of their natural counterparts. They can be very difficult to distinguish from real uncut rubies without proper testing. Synthetic rubies often have a more uniform color and may lack the subtle color variations seen in natural stones. Some may also have bubble – like inclusions or flux residues that are not typically found in natural rubies.
Glass and Other Imitations
Glass imitations are another common fake in the market. Glass can be colored to resemble the red of a ruby, but it usually has a different refractive index and density compared to a real ruby. Glass fakes are often too perfect, lacking the natural inclusions and irregularities found in real uncut rubies. They may also feel lighter in the hand compared to a genuine ruby due to their lower density. Other materials like red spinel or garnet can also be mistaken for rubies, but they have different chemical and physical properties. For example, spinel is typically a bit softer than ruby and has a different crystal structure.
Recommended Instruments and Professional Testing Advice
Loupe or Magnifying Glass
A loupe or a magnifying glass with at least 10x magnification can be a valuable tool for examining an uncut ruby. Use it to look for inclusions, which are small imperfections inside the gemstone. Natural rubies often have inclusions such as needle – like rutile, hexagonal growth lines, or other minerals trapped within the crystal. These inclusions are unique to each stone and can be a strong indication of authenticity. Synthetic rubies may have different – looking inclusions, such as uniform bubbles or signs of artificial manufacturing processes.
Gemological Laboratory Testing
For a definitive identification, it is advisable to send the uncut ruby to a reputable gemological laboratory. Gemologists at these labs use advanced techniques such as spectroscopy to analyze the chemical composition of the stone, X – ray diffraction to determine its crystal structure, and other high – tech methods. They can provide a detailed report on the authenticity, origin, and quality of the ruby. Labs like the Gemological Institute of America (GIA) or the International Gemological Institute (IGI) are well – respected in the industry. If you are investing a significant amount in an uncut ruby, getting a professional certification from such a laboratory is highly recommended to ensure you are getting a genuine and valuable gemstone.
In conclusion, identifying a genuine uncut ruby requires a combination of careful observation, basic testing, and sometimes professional help. By being aware of the key characteristics of real rubies and the common types of fakes, you can make a more informed decision when dealing with these beautiful and valuable gemstones.
