Sapphire Jewelry
Here you can learn about some of the latest equipment and challenges that gem labs face each day to positively identify gemstones so traders and consumers can buy with confidence. Gemology today is constantly focused on identifying new treatments that unscrupulous dealers apply to lower grade mine production. There are literally dozens of variables that need to be analyzed and carefully considered. High tech equipment has helped speed up the processing to identify these gemstones, but it takes years (and lots of investment) to acquire the skills of a master gemologist.
The Natural Sapphire Company uses a wide variety of gem labs around the world. There are countless low quality or even fraudulent “labs” that exist and create worthless reports; it’s very important to know the reputation of a lab before you accept their findings.
Here are some of the most common and advanced testing that the labs will undertake to identify and verify the sapphires and rubies that we work with.
Laboratory
The most important gemological-mineralogical criteria used for the characterization of gemstones are:
- Inclusion Features
- These include cavity fillings, growth features, and other characteristics within the gem that are large enough to be seen with a microscope. If more information is needed than the microscope provides, some advanced equipment can be used to report on inclusion.
- Chemical Fingerprinting
- This is a breakdown of the major, minor, and trace elements that make up the gem.
- Spectral Fingerprinting
- This is a detailed analysis of the way different types of light (particularly ultraviolet, visible, and near-infrared range light) interact with the stone. It can be used to determine the type of gem, its origin, and any treatments it has undergone.
In order to analyze the characterization of gemstones – to determine the distinctive characteristics of natural, synthetic, and treated gem materials – advanced gemstone testing requires a variety of powerful analytical tools.
Many gem materials and treatments can be identified using classical gemological equipment such as the binocular microscope, the spectroscope, and the refractometer, but detecting today’s increasingly sophisticated synthetic and treated gemstones with these tools is nearly impossible. New processes for creating synthetic gems and for artificially altering natural ones require updated methods and tools for detection. Today, we turn to more advanced scientific instrumentation to help us properly identify where a gem originated and what has been done to it.
When analyzing a gem, it is extremely important that it is not damaged by the analysis. Gems are carefully cut to achieve their beauty and are often very valuable; damaging these precious objects can significantly reduce their value and great care must be taken when examining them. Most techniques and instruments for analyzing gems do so by analyzing how different types of light interact with the gemstones. Essentially, the instruments shine different kinds of light on the gem. Sensitive detectors quantify exactly how the light has passed through, reflected off of, been absorbed by, or otherwise interacted with the gem. Different aspects of the gem’s physical and chemical composition are revealed through these processes. When we combine all of the test results we are able to create a detailed description of the stone and its past.
When analyzing a gem, it is extremely important that it is not damaged by the analysis. Gems are carefully cut to achieve their beauty and are often very valuable; damaging these precious objects can significantly reduce their value and great care must be taken when examining them. Most techniques and instruments for analyzing gems do so by analyzing how different types of light interact with the gemstones. Essentially, the instruments shine different kinds of light on the gem. Sensitive detectors quantify exactly how the light has passed through, reflected off of, been absorbed by, or otherwise interacted with the gem. Different aspects of the gem’s physical and chemical composition are revealed through these processes. When we combine all of the test results we are able to create a detailed description of the stone and its past.
All gemological methods must damage the gem as little as possible. Using light waves to gather information causes no damage to the gemstone and is considered the best technique. Occasionally, a customer would like to know other information about a gem that cannot be gathered from light testing methods. In these instances, techniques have been developed to gather the required information in the least damaging way possible. For example, to test the hardness of a gemstone, the technician must make a very small scratch in an inconspicuous place. Happily, hardness is no longer a critical component of gem analysis like it was in the past, and the scratch test is now almost never necessary.
In order to collect all the information a customer may want though, there are a few other tests that need to cause a very tiny amount of damage to an inconspicuous area of a gem. For example, to test if a gem has been artificially colored through a Beryllium diffusion process, a laser beam is used to create a tiny pinprick-sized nick (less than 200 microns in size) on an unimportant part of the surface of the stone. The material in that nick is converted by the laser into a tiny glowing cloud that detectors analyze in order to detect the artificial colorant.
Fourier Transform Infrared Spectrometer (FTIR)
A Fourier Transform Infrared (FTIR) spectrometer records the intensity of infrared light wavelengths that pass through, are absorbed by, or are reflected off when infrared light is directed at a sample. Sometimes the light is redirected by a system of mirrors to pass by the sample many times before being analyzed. The spectrum (a pattern representing the interaction of light with the sample) that results from this process represents the molecular absorption and transmission of the elements within the stone, creating a molecular “fingerprint” of the sample. Like a fingerprint, this infrared spectrum is unique to each type of material. This makes infrared spectroscopy useful for several types of analysis.
FTIR spectrometry is widely used in both research and forensic analysis in the gemological field, enabling identification of foreign substances (such as oils or resins in the case of a fracture-filled emerald) in treated gem materials. A number of synthetic gems can be distinguished from their natural counterparts by differences in their infrared spectra. Type I and Type II diamonds can also be recognized.
Top quality labs use a FTIR spectrometer for the following advanced gemstone testing:
- Detecting gems that have undergone heat treatment to alter their appearance.
- Distinguishing between synthetic and natural gems.
- Analyzing clarity enhancements of specific gems such as oils or resins in a fracture-filled emerald, or polymer impregnation in jadeite jade.
Energy Dispersive X-Ray Fluorescence Spectrometer (EDXRF)
The energy-dispersive X-ray fluorescence (EDXRF) system is used to determine a gem’s chemical composition. X-ray fluorescence (XRF) is the emission of characteristic “secondary” (or fluorescent) X-rays from a material that has been exposed to incoming high-energy X-rays. An X-ray beam illuminates and heats the sample, causing the material to emit specific X-rays that are characteristic of the major and minor chemical elements in the gem.
In general, EDXRF is widely used for elemental analysis and chemical analysis, particularly in the investigation of metals, glass, ceramics and building materials, and for research in geochemistry, forensic science and archaeology.
Top quality labs use a EDXRF spectrometer for the following advanced gemstone testing:
- Distinguishing between synthetic and natural gems.
- Analyzing trace elements to identify the geographical origin of gems.
- Detecting transition metal elements, which are responsible for the color of many gems, as well as detecting other elements that are evidence of certain treatment processes.
Ultraviolet-Visible-Near Infrared Spectrometer (UV-Vis-NIR)
An Ultraviolet-Visible-Near Infrared spectrometer analyzes light in the ultra violent, visible, and near infrared regions of the electromagnetic spectrum. Light from these ranges are directed at the gem and the results are recorded.
Absorption in the visible range directly affects the color of materials. Light from this region of the electromagnetic spectrum causes molecules to undergo certain electronic transitions and processes where light passing through the gem moves the electrons in the gem’s atoms. This determines the color of the gem by causing the material to absorb certain colors and reflect, transmit, and emit others.
The UV-Vis-NIR spectrometer is used to collect absorption and reflectance spectra from gems to help determine geographic origin and detect treatments. Top quality laboratories use a UV-VIS-NIR spectrometer for the following advanced gemstone testing:
- Analyzing trace elements to identify the geographical origin of gems.
- Detecting gems that have undergone heat treatment to alter their appearance.
Laser Induced Breakdown Spectrometer (LIBS)
Laser Induced Breakdown Spectrometers (LIBS) use a high energy laser pulse to gather information. The laser is focused to form plasma which atomizes and heats up samples. Plasma is a state of matter, like solid, liquid and gas, but is even hotter than the gas state. In a plasma, material has been superheated to temperatures so high that bonds between the atoms in the material break down, releasing ions and electrons. With this laser-created plasma, LIBS can analyze any matter regardless of its physical state, be it solid, liquid or gas, and is limited in its analytical ability only by the power of the laser and by the sensitivity and wavelength range of the spectrograph and detector used.
In analyzing gems, the spectrometer operates by focusing the laser onto an inconspicuous area on the surface of the specimen. When the laser is discharged it ablates (vaporizes) a very small amount of material (in the range of nanograms and picograms) which generates a tiny high temperature plasma plume. At the high temperatures found when the plasma is first created, the ablated material breaks down into excited ionic and atomic particles. Within a very short period of time, the plasma then expands at supersonic velocities and cools. At this point the characteristic atomic emission lines of the elements can be observed with the spectrometer. The spectrometer allows for measurement of the trace-element chemical composition of gem materials, including importantly, Beryllium.
Beryllium Treatment
In 2001, stones treated by a new process entered the market. The color of these stones resulted from diffusing the element beryllium into them from the outside in a process akin to dyeing cloth. This technique allowed one to manufacture valuable-looking yellow, padparadscha, and orange sapphires from low-value starting material. Later, it was shown that beryllium diffusion could also lighten overly dark blue sapphires. Suddenly, for sapphire treatment companies, the search for the “Holy Grail” was over; this process had the potential to dramatically rewrite the book on corundum rarity by allowing treaters to create certain valuable colors in sapphires in an almost undetectable manner. However, LIBS now allows us to detect this treatment in order to determine whether a stone’s color is a product of nature or a product of human intervention.
