GIA Diamonds and Diamond grading LATEST VERSION
QUESTIONS AND ANSWERS WITH STUDY GUIDE DETAILED AND
VERIFIED FOR GUARANTEED PASS, LATEST UPDATE 2025,2026
GRADED A
Blockchain - CORRECT ANSWER A shared, unalterable ledger used to record
transactions and track assets through a supply chain or business network.
Blocking - CORRECT ANSWER Placing the first 17 or 18 facets on a diamond,
including the crown and pavilion main facets, table, and sometimes a culet.
Bort - CORRECT ANSWER A form of industrial-grade diamond that usually occurs
as very included single crystals in a range of yellows, grays, and browns.
Bow-tie - CORRECT ANSWER A dark area across the center of an elongated
brilliant cut.
Brightfield illumination - CORRECT ANSWER Lighting a diamondfrom below to
create a bright background.
Brightness - CORRECT ANSWER The effect of all the diamond's internal and
external reflections of white light.
Brilliant cut - CORRECT ANSWER Cutting style with triangular or kite-shaped
facets that radiate from the center toward the girdle.
Brillianteering - CORRECT ANSWER Placement and polishing of the star and
upper and lower girdle facets.
Bruting - CORRECT ANSWER Forming the basic face-up outline of a round or
rounded shape diamond to prepare it for faceting.
Bulk sampling - CORRECT ANSWER Large-scale character sampling.
Carbonado - CORRECT ANSWER An aggregate of many randomly oriented
interlocking tiny diamond crystals that is the toughest form of diamond.
Carbonate - CORRECT ANSWER A class of chemical compounds that contain
carbon and oxygen.
,Catalyst - CORRECT ANSWER A substance that increases the rate of a chemical
reaction.
Cave mining - CORRECT ANSWER An underground mining technique in which
orebody is drilled beneath the surface, loosened, and collected as it falls.
Central Selling Organisation (CSO) - CORRECT ANSWER An agency designed to
purchase, sort, evaluate, and sell rough diamonds.
Character sampling - CORRECT ANSWER Testing for the size, shape, clarity, and
color of the diamonds in a deposit.
Characteristic color - CORRECT ANSWER The basic face-up color of a colored
diamond.
Clarity characteristic - CORRECT ANSWER Internal or external feature of a
gemstone that helps determine its quality.
Cleavage - CORRECT ANSWER A smooth, flat break in a gemstone parallel to
planes of atomic weakness.
Cleavage plane - CORRECT ANSWER Plane parallel to a possible crystal face,
where a diamond can split cleanly when struck.
Cleaving - CORRECT ANSWER Dividing a diamond into two or more pieces along
a cleavage plane.
CLIPPIR diamonds - CORRECT ANSWER Cullinan-like, Large, Inclusion-Poor,
Pure, Irregular, and Resorbed diamond.
Color center - CORRECT ANSWER A small defect in the atomic structure of a
material that can absorb light and give rise to a color. Structural defect that influences
an object's absorption of light and can cause its color.
Color lamellae - CORRECT ANSWER Closely spaced grain lines where color
concentrates.
Coning - CORRECT ANSWER The process of forming the pavilion angle by
gradually polishing off the extra material at different angles.
Consignment - CORRECT ANSWER A selection of goods loaned to a dealer by
another wholesaler or a gem cutter.
,Core - CORRECT ANSWER Earth's innermost layer.
Cost-plus model - CORRECT ANSWER Model in which final sale price is based
on the cost to produce the product plus a small markup.
Covalent bond - CORRECT ANSWER A chemical bond formed by two atoms
sharing electrons.
Craftsmanship - CORRECT ANSWER The care that goes into the fashioning of a
polished diamond, as confirmed by its finish.
Cratons - CORRECT ANSWER Ancient, large, and stable parts of the earth's
continental crust.
Critical angle - CORRECT ANSWER Angle between the normal and the maximum
angle of refraction, which is the largest angle at which rays inside the diamond can
escape.
Crossed polarizers - CORRECT ANSWER Two polarizers with their light-
transmitting directions aligned perpendicularly so light cannot transmit through them.
Crown angle - CORRECT ANSWER The angle formed by the bezel facets and the
girdle plane.
Crown height percentage - CORRECT ANSWER The distance from the girdle
plane to the table, expressed as a percentage of average girdle diameter.
Crust - CORRECT ANSWER The surface and outermost layer of the earth.
Crustal diamond - CORRECT ANSWER Rare diamond that forms in the
continental crust or near the earth's surface due to meteorite impact or tectonic plate
collision.
Crystal planes - CORRECT ANSWER Any set of parallel and evenly spaced
planes distributed along certain crystal directions in which atoms are most likely packed.
Crystal shape (form) - CORRECT ANSWER Geometric shape of a well-formed
crystal.
Crystal structure (lattice) - CORRECT ANSWER Regular, repeating arrangement
of atoms in a mineral.
, Crystal systems - CORRECT ANSWER Categories of crystals based on their
symmetry and internal structure.
Cuboctahedron - CORRECT ANSWER A crystal with both octahedral and cubic
faces.
Culet size - CORRECT ANSWER The size of the facet at the bottom of the
diamond where the pavilion mains meet.
Cutting style - CORRECT ANSWER The arrangement of a gem's facets.
Darkfield illumination - CORRECT ANSWER Lighting of a diamond or gemstone
from the side against a black, non-reflective background.
Defect - CORRECT ANSWER An imperfection or deviation from the ideal crystal
lattice.
Dense media separation - CORRECT ANSWER A recovery process that
separates diamonds from lighter material. Also called heavy media separation.
Depth of color - CORRECT ANSWER The combination of tone and saturation that
determines how noticeable a color is.
Depth of field - CORRECT ANSWER The distance that's clear and sharp above
and below a point you focus on with a magnifier. The distance thatÍs clear and sharp in
front of and behind the point you focus on.
Design - CORRECT ANSWER A diamond's physical shape, including its
proportions and durability, determined by decisions made during the fashioning process.
Diamantaire - CORRECT ANSWER A knowledgeable, experienced, and
successful person, usually a dealer or manufacturer, in the diamond trade.
Diamond exchange - CORRECT ANSWER A membership-based entity that
provides service and venue to facilitate diamond trading.
Diamond simulant - CORRECT ANSWER Any material that is not diamond or lab-
grown diamond, but which imitates a diamond's appearance and is used in its place.
Diamond trading company-DTC - CORRECT ANSWER The marketing and sales
arm of De Beers (the CSO was its predecessor).
QUESTIONS AND ANSWERS WITH STUDY GUIDE DETAILED AND
VERIFIED FOR GUARANTEED PASS, LATEST UPDATE 2025,2026
GRADED A
Blockchain - CORRECT ANSWER A shared, unalterable ledger used to record
transactions and track assets through a supply chain or business network.
Blocking - CORRECT ANSWER Placing the first 17 or 18 facets on a diamond,
including the crown and pavilion main facets, table, and sometimes a culet.
Bort - CORRECT ANSWER A form of industrial-grade diamond that usually occurs
as very included single crystals in a range of yellows, grays, and browns.
Bow-tie - CORRECT ANSWER A dark area across the center of an elongated
brilliant cut.
Brightfield illumination - CORRECT ANSWER Lighting a diamondfrom below to
create a bright background.
Brightness - CORRECT ANSWER The effect of all the diamond's internal and
external reflections of white light.
Brilliant cut - CORRECT ANSWER Cutting style with triangular or kite-shaped
facets that radiate from the center toward the girdle.
Brillianteering - CORRECT ANSWER Placement and polishing of the star and
upper and lower girdle facets.
Bruting - CORRECT ANSWER Forming the basic face-up outline of a round or
rounded shape diamond to prepare it for faceting.
Bulk sampling - CORRECT ANSWER Large-scale character sampling.
Carbonado - CORRECT ANSWER An aggregate of many randomly oriented
interlocking tiny diamond crystals that is the toughest form of diamond.
Carbonate - CORRECT ANSWER A class of chemical compounds that contain
carbon and oxygen.
,Catalyst - CORRECT ANSWER A substance that increases the rate of a chemical
reaction.
Cave mining - CORRECT ANSWER An underground mining technique in which
orebody is drilled beneath the surface, loosened, and collected as it falls.
Central Selling Organisation (CSO) - CORRECT ANSWER An agency designed to
purchase, sort, evaluate, and sell rough diamonds.
Character sampling - CORRECT ANSWER Testing for the size, shape, clarity, and
color of the diamonds in a deposit.
Characteristic color - CORRECT ANSWER The basic face-up color of a colored
diamond.
Clarity characteristic - CORRECT ANSWER Internal or external feature of a
gemstone that helps determine its quality.
Cleavage - CORRECT ANSWER A smooth, flat break in a gemstone parallel to
planes of atomic weakness.
Cleavage plane - CORRECT ANSWER Plane parallel to a possible crystal face,
where a diamond can split cleanly when struck.
Cleaving - CORRECT ANSWER Dividing a diamond into two or more pieces along
a cleavage plane.
CLIPPIR diamonds - CORRECT ANSWER Cullinan-like, Large, Inclusion-Poor,
Pure, Irregular, and Resorbed diamond.
Color center - CORRECT ANSWER A small defect in the atomic structure of a
material that can absorb light and give rise to a color. Structural defect that influences
an object's absorption of light and can cause its color.
Color lamellae - CORRECT ANSWER Closely spaced grain lines where color
concentrates.
Coning - CORRECT ANSWER The process of forming the pavilion angle by
gradually polishing off the extra material at different angles.
Consignment - CORRECT ANSWER A selection of goods loaned to a dealer by
another wholesaler or a gem cutter.
,Core - CORRECT ANSWER Earth's innermost layer.
Cost-plus model - CORRECT ANSWER Model in which final sale price is based
on the cost to produce the product plus a small markup.
Covalent bond - CORRECT ANSWER A chemical bond formed by two atoms
sharing electrons.
Craftsmanship - CORRECT ANSWER The care that goes into the fashioning of a
polished diamond, as confirmed by its finish.
Cratons - CORRECT ANSWER Ancient, large, and stable parts of the earth's
continental crust.
Critical angle - CORRECT ANSWER Angle between the normal and the maximum
angle of refraction, which is the largest angle at which rays inside the diamond can
escape.
Crossed polarizers - CORRECT ANSWER Two polarizers with their light-
transmitting directions aligned perpendicularly so light cannot transmit through them.
Crown angle - CORRECT ANSWER The angle formed by the bezel facets and the
girdle plane.
Crown height percentage - CORRECT ANSWER The distance from the girdle
plane to the table, expressed as a percentage of average girdle diameter.
Crust - CORRECT ANSWER The surface and outermost layer of the earth.
Crustal diamond - CORRECT ANSWER Rare diamond that forms in the
continental crust or near the earth's surface due to meteorite impact or tectonic plate
collision.
Crystal planes - CORRECT ANSWER Any set of parallel and evenly spaced
planes distributed along certain crystal directions in which atoms are most likely packed.
Crystal shape (form) - CORRECT ANSWER Geometric shape of a well-formed
crystal.
Crystal structure (lattice) - CORRECT ANSWER Regular, repeating arrangement
of atoms in a mineral.
, Crystal systems - CORRECT ANSWER Categories of crystals based on their
symmetry and internal structure.
Cuboctahedron - CORRECT ANSWER A crystal with both octahedral and cubic
faces.
Culet size - CORRECT ANSWER The size of the facet at the bottom of the
diamond where the pavilion mains meet.
Cutting style - CORRECT ANSWER The arrangement of a gem's facets.
Darkfield illumination - CORRECT ANSWER Lighting of a diamond or gemstone
from the side against a black, non-reflective background.
Defect - CORRECT ANSWER An imperfection or deviation from the ideal crystal
lattice.
Dense media separation - CORRECT ANSWER A recovery process that
separates diamonds from lighter material. Also called heavy media separation.
Depth of color - CORRECT ANSWER The combination of tone and saturation that
determines how noticeable a color is.
Depth of field - CORRECT ANSWER The distance that's clear and sharp above
and below a point you focus on with a magnifier. The distance thatÍs clear and sharp in
front of and behind the point you focus on.
Design - CORRECT ANSWER A diamond's physical shape, including its
proportions and durability, determined by decisions made during the fashioning process.
Diamantaire - CORRECT ANSWER A knowledgeable, experienced, and
successful person, usually a dealer or manufacturer, in the diamond trade.
Diamond exchange - CORRECT ANSWER A membership-based entity that
provides service and venue to facilitate diamond trading.
Diamond simulant - CORRECT ANSWER Any material that is not diamond or lab-
grown diamond, but which imitates a diamond's appearance and is used in its place.
Diamond trading company-DTC - CORRECT ANSWER The marketing and sales
arm of De Beers (the CSO was its predecessor).
