DDG Ass 19 Tools and Instrumentation PDF

DDG Ass #19 Tools and Instrumentation Tools Of the Trade: - A diamantaire is a knowledgeable, experienced professional, typically a dealer or manufacturer, in the diamond trade. -Many of the industry’s foremost diamantaires started out sorting and matching small diamonds. -Standard gemological equi...

DDG Ass #19 Tools and Instrumentation Tools Of the Trade: - A diamantaire is a knowledgeable, experienced professional, typically a dealer or manufacturer, in the diamond trade. -Many of the industry’s foremost diamantaires started out sorting and matching small diamonds. -Standard gemological equipment: These include—but are not limited to—tweezers, a scoop, a sorting pad, a matching tray, a loupe, a millimeter gauge, sieve sets, hole gauges, and an electronic scale. Handling, Sorting, and Measuring Diamonds: - Organization is key when working in the diamond industry. -Many use stone papers—folded parcel papers that come in standard sizes to fit into stock boxes—hold and protect single diamonds, matched suites, and parcels. -Detailed information about the diamonds inside—size, weight, cost, and so on—is written on the front of each paper. Handling Stone Papers: - Stone papers come in a variety of sizes and colors, and consist of two or three layers of paper folded together. - he outside layer is typically white and opaque, while the innermost layer is a thin, translucent liner called a flute. - The color of the flute affects the apparent color of the diamonds it holds, Light blue flatters colorless and near-colorless diamonds, Off-white or light yellow flutes make yellowish or brownish diamonds look better. Tools to Handle, Sort and Measure: - A pair of tweezers and a cleaning cloth are essential. Tweezers with medium points are best for most purposes. -To work with parcels, you need a scoop and a sorting pad. A scoop is a small metal shovel that’s thin enough to slide easily under tiny stones. - A sorting pad is a pad of heavy white paper that serves as a background for sorting parcels of gems. -A matching tray is another convenient surface for comparing and matching gems to create stone sets. Typically it’s a small white plastic tray indented with grooves for various diamond sizes. -Examining and grading diamonds requires a consistent source of light. The most widely accepted and available lighting for color grading diamonds is daylight-equivalent fluorescent light. -a good-quality 10x triplet loupe that’s corrected for color and distortion. -a calculator to calculate profit margins, sales prices, and average gem weights, and a memo pad for recording - The millimeter gauge is used to measure diamond dimensions, gauge’s jaws close around a diamond’s girdle, it registers the diameter to the nearest 0.01 mm. A millimeter gauge can also measure a stone’s depth, as long as the stone is unmounted or in a mounting with a hole in the back. - A sieve set is useful for sorting large quantities of small, round diamonds. A sieve set usually consists of a holder and a series of interchangeable plates perforated with holes in specific sizes. -Dealers use sieves to sort small diamonds—especially small single cuts in sizes like 150, 180, and 200 to the carat Weighing Diamonds: -Most scales have a leveling mechanism, which typically consists of adjustable feet and a liquid-filled capsule with a gas bubble inside. - Once you’ve leveled the scale, it must be calibrated using the weight provided - Keep the scale on a firm, vibration-free surface, away from foot traffic as well as drafts and heat sources such as windows, heating ducts, and cooling fans. Even direct sunlight can create enough of an air current to affect a scale’s accuracy. Most scales have sliding glass doors to protect from drafts. Matching Diamonds: - Weight, color, clarity, and cut are all considerations in matching, the human eye easily detects inconsistencies like slight differences in face-up color, differently sized table facets, or different girdle diameters. -Color and face-up appearance are the most important characteristics in matching diamonds for jewelry. -Color: Just compare the diamonds face-up against a neutral background. -Matching face-up appearance means making sure that table sizes and reflection patterns are the same. -Use the flash method to compare table sizes, and check the reflection patterns through each gem’s crown. Matching Diamonds continued...... - Clarity matters when matching large diamonds in the “I” clarity range. This range has much greater variations in appearance among individual diamonds, simply because it has a greater variety of possible clarity characteristics. -The smaller the diamonds, the less matching needed. Just make sure they’re all the same size, and flip them onto their tables to compare girdle diameters. -For gems of about 0.025 ct. and larger, look at them face-up on a matching tray and compare table sizes and reflection patterns. -Diamonds 0.05 ct. and above require more precise matching. Look at stones’ color and clarity characteristics. -To match a set of accent stones with a large center stone, it’s best to choose the center stone first. Advance Instrumentation: - Gemologists operate advanced instruments to collect data on diamonds that can help conclusively identify their nature and color origin, among other things. Further examination and interpretation of the data by laboratory professionals is required. UV-Vis-NIR Spectroscopy: - Most advanced testing methods measure a diamond’s response to electromagnetic radiation. -UV-Vis-NIR (ultraviolet/visible/near-infrared) absorption spectroscopy measures a diamond’s absorption of visible light and portions of the ultraviolet and infrared regions close to the visible range. - The highly sensitive instrument used to analyze a gem’s radiation absorption is called a spectrometer. This instrument is an accurate wavelength position for each peak and records features outside the visible range -An instrument called a spectroscope can also reveal a diamond’s absorption spectrum,A spectroscope is much less sensitive than a spectrometer. -Prior to analysis of the diamond by the UV-Vis-NIR spectrometer, liquid nitrogen is used to cool the stone to -196°C. Diamond’s physical properties make cooling to this temperature possible; -Cooling the diamond sharpens the spectral absorption peaks and allows gemologists to identify the optical defects in the diamond. -The UV-Vis-NIR spectrometer can test only one diamond at a time. Color Cause Determination: - UV-Vis-NIR absorption spectroscopy is vital for colored diamond identification because it assists gemologists in determining the color centers responsible for a diamond’s color. Infrared Spectroscopy : -A Fourier-transform infrared (FTIR) spectrometer measures a diamond’s absorption of infrared energy and portions of the visible and radio wave regions of the electromagnetic spectrum. -One major advantage of an FTIR spectrometer is its speed: It provides results in a fraction of a second. -An FTIR spectrometer measures and records what portion of energy within the infrared range is absorbed by a diamond. A computer interprets the reading and transforms it into an absorption spectrum. Diamond Type: -Infrared spectroscopy is the only way to accurately categorize a diamond by type. -The presence or absence of absorption caused by boron and/or nitrogen—and whether the nitrogen is isolated or aggregated—in the infrared absorption spectrum of a diamond determines its type. -Diamond type can reveal much about a diamond and its possible treatment and growth histories. Photoluminescence Spectroscopy -Photoluminescence (PL) spectroscopy: It measures the light emitted by the diamond with more detail and higher detection capability. -PL spectroscopy allows for extremely precise detection of trace concentrations of these defects, and this method is unmatched by other nondestructive characterization techniques -PL spectroscopy can identify defects that might go undiscovered with classic UV-Vis-NIR and FTIR spectroscopy. Photoluminescence Spectroscopy continured...... - PL spectroscopy uses a high-power laser, a microscope, a high-resolution spectrometer, and a computer. -The laser is directed to a diamond through a microscope. The resulting luminescence—light emitted by the diamond—is measured by a high-resolution spectrometer. -A computer transforms the reading into a spectrum that indicates what wavelength of energy is emitted and how much. A graph displays the spectrum as wavelength in nanometers (horizontal axis) versus intensity (vertical axis). Photoluminescence Mapping: - gemologists are able to collect and map PL data across the entire surface of a diamond. This technique shows subtle distinctions in defect concentrations and is known as photoluminescence mapping. -PL mapping allows gemological labs to identify lab-grown diamonds and color treatments, even with continued advancements in synthesis and treatment technologies. High-Energy UV Imaging: - While most diamonds do not fluoresce to shortwave or longwave UV, all diamonds show fluorescence at the ultra-shortwave UV wavelength -The DiamondView imaging microscope operates at the level of ultra-shortwave UV radiation. This is a lower wavelength and higher energy than shortwave UV typically used for fluorescence observations in routine gemological work. -De Beers developed the DiamondView to distinguish natural from HPHT lab-grown diamonds in the mid-1990s. -The DiamondView shows fluorescence only from the near-surface region, not the entire diamond. It is ideal for revealing a diamond’s growth patterns -The aperture—the opening through which light enters the camera—must be adjusted for an acceptable field of view. If the aperture is very small, then the exposure—the amount of time light has to enter the camera— must be much longer, so there is a tradeoff to get the best results. Identifying Lab Grown Diamonds: - The vast majority show blue fluorescence, with most natural type Ia diamonds in the D-to-Z color range showing a pattern similar to tree rings. Most natural type II diamonds show a blue spiderweb pattern known as dislocation bundles. - The cuboctahedral growth structure of HPHT lab-grown diamonds is quite distinct from the octahedral structure of natural diamonds -the most common and distinctive feature that indicates CVD lab-grown diamonds is striations. CVD lab- grown diamonds grow as a thin film, layer by layer, which generates terraces and risers. A Brilliant Puzzle: - In November 2015, Lucara Diamond Corp. discovered five large diamonds at its Karowe mine in Botswana. -Lucara claimed that the 374-ct. diamond was once attached to the Lesedi La Rona. It was believed that all five of these diamonds were one large piece of rough weighing at least 2,774 cts. before volcanic eruptions and/or mining processes split it up. - Due to the similarity in their visible characteristics—including cleavage faces, metallic inclusions, and iron oxide staining—and when the diamonds were mined, these five stones were thought to be related. But this was only speculation before the diamonds were subjected to advanced testing.