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Grading 315 complete solutions latest
GIA GEM 230 - Diamonds & Diamond
Grading 315 complete solutions latest
The diamond rush began with the discovery of _______. - ANSWER the Star of South Africa in 1869
Cecil Rhodes wanted to stabilize diamond prices, so he started by _______. - ANSWER trying to control production
Cecil Rhodes established _______ in 1888 to direct mining operations. - ANSWER De Beers Consolidated Mines Ltd.
When it couldn't own every mine, De Beers began buying _______ from other producers to safeguard diamond prices and ensure market stability. - ANSWER rough
_______ heightened demand for industrial diamond rough. - ANSWER Military needs during WWII
Rough is sorted into categories based on _______. - ANSWER size, shape, clarity, and color
At a sight, the _______ presented a customized selection of diamonds to each sight holder for acceptance. - ANSWER CSO
Central Selling Organization (CSO) - ANSWER an agency designed to purchase, sort, evaluate, and sell rough diamonds
Digger - ANSWER an independent diamond prospector
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Dry Diggings - ANSWER a prospector's term for diamond deposits away from water
London Diamond Syndicate - ANSWER a group of diamond merchants that united in 1890 to buy and sell rough diamonds
Diamond Pipeline - ANSWER the path diamonds followed from the mine to the consumer
Sight - ANSWER trading event where selected clients buy rough diamonds
Sightholder - ANSWER a diamond manufacturer or dealer invited by De Beers to buy rough diamonds
Single-Channel Marketing - ANSWER a direct, centrally controlled marketing route for rough diamonds
Special - ANSWER a rough diamond over 10.80 cts. sold separately to a slight holder who specialized in larger stones
The CSO controlled diamond prices by _______. - ANSWER buying and holding supplies until demand increased
Beneficaton helps countries exercise _______ control over their natural mineral resources. - ANSWER greater
De Beers' advocacy of _______ had a more profound impact on the diamond market than its advocacy of branding. - ANSWER corporate responsibility
The future of the diamond market in manufacturing and consumption may be in _______. - ANSWER Asia, especially China and India
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_______ kimberlites actually contain diamonds. - ANSWER Very few
Cratons - ANSWER ancient, large, and stable parts of the earth's continental crust
Emplacement - ANSWER a geologic process that delivers materials (sometimes diamonds) to the surface
Igneous Rock - ANSWER a category of rocks formed from a molten state
Kimberlite - ANSWER an igneous rock that transports diamonds to the surface
Lamproite - ANSWER an igneous rock, rarer than kimberlite, that transports diamonds to the surface
Mantle - ANSWER layer between the earth's crust and its core
Pipe - ANSWER a deep vertical formation at the earth's surface that results from a kimberlite or lamproite emplacement
Subduction - ANSWER process in which two crustal plates collide, forcing one under the other
Diamond exploration specialists start by looking for the _______ parts of the earth's crust. - ANSWER oldest
Most diamonds mined today come from _______. - ANSWER pipes
Alluvial Deposit - ANSWER a deposit where gems are eroded from their source rock, then transported away from the source and further concentrated
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Bulk Sampling - ANSWER large-scale character sampling
Character Sampling - ANSWER testing for the size, shape, clarity, and color of the diamonds in a deposit
Gravity Sorting - ANSWER separating heaver materials (diamond) from a test sample
Indicator Minerals - ANSWER minerals formed together with diamonds at great depths and brought to the surface by the same kimberlites or lamproites
Marine Deposit - ANSWER secondary diamond deposit carried by rivers or streams to the ocean floor or shoreline
Microdiamond Testing - ANSWER screening for the presence of tiny diamond in a sample
Ore Grade - ANSWER concentration of diamond in a potentially mineable deposit
Primary Deposit - ANSWER gems found in the rock that carried them to the surface
Secondary Deposit - ANSWER gems found away from their primary source
Improved technology caused a shift in emphasis from _______ to _______ mining. - ANSWER alluvial to primary
_______ holds perhaps the largest marine diamond deposits in the world. - ANSWER Namibia
_______ was the world's only major diamond source until the 18th century. - ANSWER India
Grading 315 complete solutions latest
Overburden - ANSWER sand, gravel, or rock that covers a diamond pipe; must be removed to reach diamond-bearing ore
Primary Crushing - ANSWER reduction of newly mined ore to a manageable size
Recovery - ANSWER any method used to separate diamonds from ore or alluvial sediments
Scrubber - ANSWER an apparatus that washes away dirt and clay from diamond-bearing ore
X-Ray Separation - ANSWER a recovery method that uses X-rays to detect diamonds and an air jet to remove them from ore
Diamond's atoms are _______ closely bonded than the atoms of any other natural material. - ANSWER more
The most common habit of gem diamond is the _______, but being perfectly shaped is rare. - ANSWER octahedron
Diamonds belong to the _______ or _______ crystal system, the most symmetrical of the crystal systems. - ANSWER cubic or isometric
_______ is the most important factor in a rough gem diamond crystal's potential value. - ANSWER Shape
_______ planes provide the most efficient sawing directions for diving large, regularly shaped crystals. - ANSWER Cubic
The _______ is the most common twinned diamond crystal. - ANSWER macle
Grading 315 complete solutions latest
Diamond rough's potential as a faceted gem depends on its _______, _______, and _______. - ANSWER shape, clarity, and color
The _______, _______, and _______ planes are the most important directions to a diamond cutter. - ANSWER cubic, octahedral, and dodecahedral
Aggregate - ANSWER a solid mass of individual, randomly oriented crystals, inter grown or held together by a natural binding agent
Cleavage Plane - ANSWER plane parallel to a possible crystal face, where a diamond can split cleanly when struck
Covalent Bond - ANSWER a chemical bond formed by two atoms sharing electrons
Crystal - ANSWER solid matter with atoms arranged in a regular, repeating pattern
Crystalline - ANSWER composed of crystals or related to crystals
Crystal Planes - ANSWER internal directions parallel to a mineral's unit cell surfacea
Crystal Shape (form) - ANSWER geometric shape of a well-formed crystal
Crystal Structure (lattice) - ANSWER regular, repeating arrangement of atoms in a mineral
Crystal Systems - ANSWER categories of crystals based on their symmetry and internal structure
Doubling - ANSWER the appearance of double images of a gemstone's facet junctions on the side opposite the viewer
Grading 315 complete solutions latest
Trace Elements - ANSWER atoms in a gem that aren't part of its essential chemical composition
Twinned Crystal - ANSWER crystal consisting of two or more inter grown crystals with opposing crystal directions
Unit Cell - ANSWER smallest group of atoms with the characteristic chemical composition and the basic crystal structure of a mineral
Visible light is a _______ portion of the electromagnetic spectrum. - ANSWER small
_______ light is combination of all the spectral colors. - ANSWER White
The _______ always equals the angle of reflection. - ANSWER angle of incidence
A material's _______ affects the speed of light that passes through it. - ANSWER optical density
Light rays that enter at the maximum angle of refraction form a _______ inside the diamond. - ANSWER critical angle cone
The higher a gem's RI, the _______ its critical angle. - ANSWER smaller
White light breaks up into its _______ when it passes at an angle into a denser material. - ANSWER component colors
Each spectral color has its own _______ and _______. - ANSWER RI and angle of refraction
All diamonds have the same _______ value, but differences in diamond cut bring out differing amounts of fire. - ANSWER dispersion
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A diamond's _______ pattern reveals almost all of the cutter's fashioning choices. - ANSWER face-up
_______ lighting helps you evaluate a diamond's brightness and pattern, while _______ helps you evaluate its fire. - ANSWER Diffused fluorescent, spotlighting
Adamantine Luster - ANSWER the highest degree of luster possible in a transparent material
Angle of Incidence - ANSWER the angle at which a ray of light strikes a surface, measured from the normal
Angle of Reflection - ANSWER the angle between the normal and a reflected ray of light
Brightness - ANSWER the effect of all the diamond's internal and external reflections of white light
Critical Angle - ANSWER angle between the normal and the maximum angle of refraction, which is the largest angle at which rays inside the diamond can escape
Dispersion - ANSWER an optical property that's the difference between the RI values of specific violet and red wavelengths of visible light for a given material
Fire - ANSWER the flashes of color you see in a polished diamond
Luster - ANSWER the appearance of a material's surface in reflected light
Normal - ANSWER an imaginary line perpendicular to the point where a ray of light strikes the surface
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Bruting - ANSWER forming the basic face-up outline of a round or rounded-shape diamond to prepare it for faceting
Cleaving - ANSWER dividing the diamond into two or more pieces along a cleavage plane
Dop - ANSWER a holder that secures a diamond during sawing, bruting, or polishing
Kerf - ANSWER a notch scratched into diamond rough to prepare it for cleaving
Old European Cut - ANSWER an early brilliant cut with a circular girdle
Old-Mine Cut - ANSWER an early cushion-shaped brilliant with a high crown, deep pavilion, and 58 facets including a large culet
Planner - ANSWER the person who decides where to mark diamond rough for fashioning into the most profitable polished gem
Polishing - ANSWER placing and finishing facets on a rough diamond
Sawing - ANSWER dividing diamond rough into sections, either mechanically or by laser
Scaife - ANSWER a rapidly spinning horizontal disc coated with diamond powder, used to polish diamond rough
Single Cut - ANSWER a simple diamond cut, with a table, eight crown facets, eight pavilion facets, and sometimes a culet
Grading 315 complete solutions latest
Tang - ANSWER a device that holds the dop and allows polishers to adjust and maintain a diamond's angle during polishing
The first polished diamonds appeared in Europe around _______. - ANSWER 1380
Early cutters used boards treated with _______ and _______ to shape diamond rough. - ANSWER diamond dust and olive oil
Cutters apply the _______ cut to fancy shapes to get maximum profit from oddly shaped or low-color rough. - ANSWER brilliant
_______ on the rough's surface help determine its internal crystal directions. - ANSWER Growth marks
The _______ gave cutters the ability to manufacture more than one fashioned stone from a piece of octahedral rough. - ANSWER rotary saw
_______ is a crucial stage because it establishes the gem's basic symmetry. - ANSWER Blocking
Bast - ANSWER frosted rough diamond
Cleaver - ANSWER a person who cleaves, or splits, a diamond along a cleavage plane
Cross Worker - ANSWER a person who performs the cross-working operating during diamond polishing
Cross Working - ANSWER placing the bezel and pavilion facets on round and fancy shapes
Foss - ANSWER irregular furrow or groove in the surface of a diamond, characteristic of diamond crystals in the gray color range
Grading 315 complete solutions latest
Water - ANSWER a historic term once used in Europe to describe either the color or the transparency of a diamond
Blemish - ANSWER clarity characteristic that's confined to the surface of a polished gemstone
Clarity Characteristic - ANSWER internal or external feature of a gemstone that helps determine its quality and establish its identity
Darkfield Illumination - ANSWER lighting of a diamond from the side against a black, non-reflective background
Depth of Field - ANSWER the distance that's clear and sharp above and below a point you focus on with a magnifier
Face-Up - ANSWER a position that orients a gemstone's crown facets and table toward the viewer
Feather - ANSWER a trade term for any break in a diamond
Flash Effect - ANSWER a flash of changing color seen in a fracture-filled diamond when you look parallel to the filled inclusion and rock the diamond back and forth under magnification
Fracture Filling - ANSWER treatment that involves injecting a molten glass substance into a diamond's surface-reaching feathers or laser drill-holes
Inclusion - ANSWER clarity characteristic totally enclosed in a polished gemstone or extending into it from the surface
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If a trained grader can't see a clarity characteristic at 10X, it _______ affect the clarity grade. - ANSWER doesn't
A _______ can be considered a sign of efficient cutting. - ANSWER natural
Crystal (Xtl) - ANSWER a mineral crystal contained in a diamond
Needle (Ndl) - ANSWER a long, thin crystal that looks like a tiny rod at 10X
Pinpoint (Pp) - ANSWER a very small included crystal that looks like a tiny dot at 10X
Cloud (Cld) - ANSWER many tightly grouped pinpoints that might be too small to distinguish individually at 10X but together have a hazy appearance
Internal Inclusions - ANSWER - crystal
Internal Inclusion Resulting from Crystal Structure - ANSWER - twinning wisp
- internal graining
- grain center
Twinning Wisp (TW) - ANSWER a series of pinpoints, clouds, or crystals that forms in a diamond's growth plane; associated with crystal distortion and twinning planes
Grading 315 complete solutions latest
Patch of Color (Patch) - ANSWER naturally occurring radiation stain left on a polished diamond; typically a blemish, but can be an inclusion if it extends into the stone when viewed at 10X
Chip (Ch) - ANSWER a shallow opening caused by damage to the stone's surface; typically occurs at a girdle edge, facet junction, or culet
Indented Natural (IN) - ANSWER a portion of the rough's original surface, or skin, that dips below the polished diamond's surface at 10X
Cavity (Cav) - ANSWER 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
Inclusions Caused by Treatment - ANSWER - laser drill-hole
Laser Drill-Hole (LDH) - ANSWER a tiny, surface-reaching tunnel produced by a laser light beam
Internal Laser Drilling (ILD) - ANSWER laser drilling within a diamond that doesn't reach the surface
Blemishes Caused by Wear - ANSWER - nick
Nick (Nck) - ANSWER a small notch on a facet junction with no readily apparent depth at 10X, usually along the girdle edge or at the culet
Grading 315 complete solutions latest
Abrasion (Abr) - ANSWER a series of minute scratches or pits along the facet junctions of a fashioned diamond; gives the edge a white or fuzzy appearance
Scratch (Scr) - ANSWER a thin, dull white line across the diamond's surface; shows no apparent depth at 10X
Blemishes Introduced in the Cutting Process - ANSWER - extra facet
- polish mark
- lizard skin
- polish lines
- burn
- dop burn
- rough girdle
- pit
Extra Facet (EF) - ANSWER a small facet that's not required by the cutting style, placed without regard for the diamond's symmetry; most often found near the girdle
Polish Mark - ANSWER a feature that resembles an extra facet but lacks a distinct or straight facet junction
Lizard Skin (LS) - ANSWER wavy or bumpy area on the surface of a polished diamond
Polish Lines (PL) - ANSWER fine, parallel grooves and ridges left by polishing; can occur at any facet but do not cross facet junctions; transparent or white
Burn (Brn) - ANSWER hazy surface area that results from excessive heat during polishing or occasionally from a jeweler's torch
