Diamond Clarity Grading PDF

DDG ASS #9: Finding & Identify Clarity -Clarity grading is one of the most important aspects of GIA's grading system. -clarity characteristics. Others—including customers and even some jewelers—call them flaws or imperfections Looking Clarity Characteristics: -There are two types of clarity charact...

DDG ASS #9: Finding & Identify Clarity -Clarity grading is one of the most important aspects of GIA's grading system. -clarity characteristics. Others—including customers and even some jewelers—call them flaws or imperfections Looking Clarity Characteristics: -There are two types of clarity characteristics: -Inclusions are features that are enclosed within a gemstone or extend into it from the surface. -Blemishes are external features, confined to a gemstone’s surface. -To grade clarity, graders examine a stone in a systematic way, find its clarity characteristics, identify them, and judge their impact Examining Stones: -first impression, look at the stone face-up through a fully corrected jeweler’s loupe or a binocular gemological microscope at 10x magnification. -Use only a triplet loupe that’s been fully corrected for color distortion, called chromatic aberration, and for linear distortion, called spherical aberration, these corrected lenses eliminate these distortion -Chromatic aberration causes a rainbow effect around the viewing field -Spherical aberration causes straight lines to appear to bend at the edges of the viewing field. -Achromatic lenses are corrected for color, and aplanatic lenses are corrected for spherical aberrations. -Darkfield illumitation makes the inclusions stand out -Brightfield illumintation can make the inclusion stand out as noticable black objects -As you focus on a point, anything within a certain distance above and below that point will also be clear and sharp. That distance is called the depth of field, As you increase magnification, the depth of field gets shallower -The closer the inclusion is to its reflection, the closer it is to the surface. -The strong refraction of diamond causes you to see two or more images of the same characteristic when you look through adjacent facets. These are called prism images. -Considering what area is in focus when adjusting the microscope can help determine if its a blemish or an inclusion -Another way to distinguish between surface and totally enclosed characteristics is to position the stone so the light source is at an angle to the facet. Types of Clarity Characteristics: -Internal Inclusions: -A crystal (Xtl) is a mineral crystal contained in a diamond. - Researchers have identified more than 24 different mineral crystals that might be found in diamonds. -The most common are smaller diamond crystals, but you’ll also see olivine and, occasionally, garnet crystals. -A needle (Ndl) is a long, thin crystal that looks like a tiny rod at 10x magnification, and can appear white, bright, or dark. -A pinpoint (Pp) is a very small crystal that looks like a tiny dot at 10x. Pinpoints are most often white, but they can occasionally be dark, together they look like misty white or gray patches, or like tiny flecks of white powder. -A cloud (Cld) consists of many tightly grouped pinpoints, some clouds look like a light haze, while others are dense and almost impossible to see through. -If a cloud is large and dense, it can reduce a diamond’s transparency and therefore its brilliance and beauty. -The twinning wisp (TW) is one of them. It’s a series of pinpoints, clouds, or crystals that forms in a twinning plane, they can appear flat and ribbon-like, and usually radiate out from the diamond’s center. -Internal graining (IG) is also caused by irregularities in crystal growth, their appearance can take the form of lines or angles, and it might be transparent, whitish, colored, or reflective, they can also look like a thin sheet of reflective plastic inserted into the stone, or like fine white or colored streaks. -Internal graining that appears colorless or transparent has no effect on the clarity grade. -A grain center (GC) is a type of internal graining that consists of a small concentrated area of crystal growth distortion and can be white or dark, and it might have a thread-like or pinpoint-like appearance, or look like transparent tornadoes caught deep inside the diamond. -Surface Reaching Inclusions: -A feather (Ftr) is a general term for any break in a diamond. It’s called a gletz in many countries. -Cleavage is a break that occurs in a cleavage plane, and a break in any other crystal direction is called a fracture. -feather might look shiny and white, glossy, or transparent, depending on the viewing direction. -An etch channel (EC) is an angular opening that starts at the surface of the diamond and extends into it and can be straight or curved, shallow or deep, and it often has striations perpendicular to its length. Surface Reaching Inclusions continue........ - A bearded girdle (BG) consists of minute or minor feathers running perpendicular to a bruted girdle, and lightly bearded girdle has a few very fine feathers scattered around the diamond’s perimeter. - heavily beareded has so many feathers that they create a fuzzy gray fringe all the way around the stone. - A bruise (Br) is a tiny area of impact accompanied by very small root-like feathers visible at 10x magnification, can appear cottony in texture as it radiates into the diamond. A bruise is sometimes called a percussion mark. - A knot (K) is an included diamond crystal that extends to the surface after fashioning, sometimes look like slightly raised areas on a facet or group of facets. -A knot is oriented differently from its host diamond, so it can cause problems and slow the polishing process. - Patch of color (Patch) is a naturally occurring radiation stain on a polished diamond, and it’s originally green, but heat from the cutting process can turn it brown. - Patches of color are usually considered blemishes, but if you can see that they penetrate the diamond at 10x, they’re inclusions. -A chip (Ch) is a shallow opening on the surface, located at the girdle edge, facet junction, or culet, and chips typically have rounded outlines and steplike breaks, similar to the ridges on a shell. - A cavity (Cav) is an opening on the surface that occurs when part of a feather breaks away, or when a crystal drops out or is forced out, typically during polishing. -An indented natural (IN) is a portion of the original crystal surface, or skin, that dips below the polished diamond’s surface,The original surface might have growth marks such as trigons or parallel grooves. -The laser drill-hole (LDH) is a tiny tunnel produced by a laser beam. The tunnel extends from the surface to a dark included crystal. - Internal laser drilling (ILD) is a method that creates a surface-reaching feather or expands a pre-existing feather around a dark inclusion. - Laser drilling can improve a diamond’s appearance and marketability. You must disclose the presence of a laser drill-hole. -Laser drill-holes and surface-reaching feathers are sometimes filled with a molten glass substance in a treatment called fracture filling. - Fracture filling treatment leaves a telltale sign called the flash effect that can help. Look for the irregularity, & then rock the diamond back & forth the flash of color that changes to a second color when you tilt the stone. Blemishes: - A nick (Nck) is a small notch on a facet junction, usually along the girdle edge or at the culet. - An abrasion (Abr) is a series of minute scratches or pits along a facet junction giving a white or fuzzy appearance, also when one diamond rubs against another in a stone paper and described as “paper worn.” -A scratch (Scr) is a thin, dull white line across the diamond’s surface. It can be either curved or straight. - An extra facet (EF) is a facet that’s not required by the cutting style. Though extra facets might occur anywhere on the diamond, they’re most often located at the girdle. -Cutters sometimes intentionally place tiny extra facets near the girdle edge on the pavilion to determine polishing directions for the star facets and upper and lower half facets. -Those extra facets might be removed, or they might remain after fashioning is complete. -A cutter might also intentionally add an extra facet to remove or reduce an inclusion. -A feature that resembles an extra facet but lacks a distinct or straight facet junction is called a polish mark. -Lizard skin (LS) is a wavy or bumpy area on the surface of a polished diamond. It occurs when the cutter polishes too close to the octahedral plane or parallel to it. -Polishing sometimes leaves fine, tiny parallel grooves and ridges called polish lines (PL) and occur on any facet, but they don’t cross facet junctions. -Burn (Brn) is a hazy surface area that results from excessive heat applied during polishing, or occasionally from a jeweler’s torch. -. A surface burn caused by excessive heat at the location where the dop touches the diamond is referred to more specifically as a dop burn (Dop). Blemishes continued........... - A rough girdle (RG) indicates the irregular, pitted, or granular surface of a bruted girdle, A rough girdle looks coarse, like the surface of a sugar cube. - A pit (Pit) is a small opening that usually looks like a tiny white dot. Pits usually result when pinpoint inclusions are pulled from the diamond during the polishing process. -A laser manufacturing remnant (LMR) is a characteristic created during a laser manufacturing process, usually marking or sawing, that remains on the surface of a finished diamond. - Sometimes the laser penetrates into the diamond, causing an internal or surface-reaching fracture. The fracture is considered an inclusion. -A natural (N) is a portion of the rough diamond’s original surface, or skin, that remains on a fashioned stone, it sometimes shows growth marks, and it often has an uneven surface. -When a cutter leaves a natural in place to save weight, it’s considered a sign of efficient cutting. -Naturals may be anywhere on a diamond, but they’re usually on or near the girdle, most often on the pavilion side. -Surface graining (SG) consists of one or more transparent lines on the surface of a finished diamond, It’s a visible indication of irregularities in the diamond’s crystal structure,surface graining might change direction within a facet, cross facet junctions, or run in a direction different from polish lines. -Surface graining is almost impossible to remove because it’s part of a diamond’s distorted crystal structure. Other Features: - a diamond might be inscribed with text, numbers, or even a logo for purposes of identification or branding. - An inscription has no effect on clarity regardless of its location, as long as it’s confined to the surface when viewed at 10x. - An inscription with depth visible at 10x or that is totally enclosed within the diamond is considered an inclusion and can affect the clarity grade. -Sometimes a manufacturer adds surface grooves to secure a diamond in an “invisible” mounting—one without prongs.