Gregory Diamond
12-05-2005, 05:18 PM
Below is a glossary of common terms used in sorting and dealing in rough diamonds.
Aggregate diamonds: Diamonds that have crystallized together with some apparent symmetry. Crystals appear as crosses, triangles, complex shapes or an amorphous mass.
Big sizes: Diamond rough weighing four grains or more.
Browns: The categories of brown-tinged diamonds ranging from finest light brown to good light brown, light-brown, brown and dark brown.
Canary:Golden-yellow diamonds that fluoresce in yellow-orange colors. These are distinct from Cape series yellows, which may fluoresce blue, or not at all.
Cape: Diamonds with colors ranging from the finest whites to yellowish hues.
Cleavages: All diamonds that lack a definite crystalline form, including broken octahedrons and dodecahedrons. Cleavages may be quite large ? the Cullinan is one example.
Cleaving: A process for dividing the diamond rough in two in order to remove impurities before polishing. The cleaver makes a notch, called a kerf, in the stone, then inserts a cleaving knife into the notch and strikes it with a cleaving hammer, causing the stone to split cleanly along a cleaving plane which is inherent in the crystal structure of the stone.
Coated diamonds: Diamonds that are covered by an opaque ?skin.? Polishing a window is often necessary to determine the true color of the diamond.
Collection: The second highest color category for a Cape series diamond, indicating a white stone.
Cube: A six-sided type of rough diamond. Usually these are distorted and have marked surfaces, making them more useful for industrial purposes.
Diamond: An extremely pure form of carbon crystallized into a cubic system. Diamonds sometimes absorb small amounts of other elements, including boron, nitrogen and hydrogen. Diamonds are the hardest substance, rating 10 on the Mohs hardness scale.
Dodecahedron: A diamond crystal that contains 12 facets, formed by resorption of the edges of the octahedron by the kimberlite or lamproite volcanic material. Because they are formed in this manner, their edges are often rounded.
Extra collection: The top category of the Cape series, indicating the finest white colors.
Flat: A common variation in octahedrons in which there are two parallel faces that have developed preferentially so that flat crystals result. Flats vary greatly in thickness. Some can be polished into gem quality diamonds, and some are thin enough to use as watch crystals.
Gem quality: Diamond rough capable of being polished for use in jewelry.
Grain: The measure of the size of rough. Each grain is equal to 0.25-carats, so that four grains equal one carat. Grain is also the term for the direction of the diamond crystal. Determining the grain determines how to cleave or saw the diamond.
Industrial quality: Diamonds that cannot be used in jewelry because of their small size, poor color, deformed or broken crystal shape or complicated crystal structures that cannot be polished.
Kimberlite: A rare kind of igneous rock, one of only two that host primary diamond deposits.
Lamproite: Rarer than kimberlite, this is second kind of mineral that hosts diamonds. The Argyle diamond mine is the best known example of a lamproite diamond deposit.
Macles: Created when one-half of an octahedral twin crystal is rotated 180 degrees in relation to the other half. The result appears like a flat crystal indented along the sides.
Makeable: A diamond crystal that is polished whole, without any sawing or cleaving.
Mesh size: Numerical categories of diamond rough based on a series of sieve plates numbered from 0 to 40, with 40 having the largest holes. For example, stones designated as ?+10? are those too large to sift through the holes of the number ?-10? sieve. Those designated as ?-10? do fall through.
Naat: A junction at which one diamond crystal is embedded inside another diamond crystal.
Octahedron: The most common form of diamond crystal, with eight triangular faces.
Second Cape: The lower end of the Cape series, indicating a stone with more pronounced yellowish coloring.
Shapes: In sorting, the group of rough that includes diamond crystals which are not symmetrical.
Small sizes: Rough weighing less than four grains.
Sorting: The process of separating rough into broad categories and then into more specific subgroups for the purpose of marketing the stones.
Stones: The category of rough that includes octahedrons, cubes and dodecahedrons that are near perfect in form.
Tetrahedron: Diamonds that appear in this form are usually octahedra that have been flattened or distorted.
Triangles: Macles with rounded corners.
Twinned crystals: Diamonds that consist of two or more crystals that appear as a single mass. Most are small octahedrons joined to another octahedron or dodecahedron, or cubes joined together. Because the grain of each component is oriented in a different direction, such stones present a challenge for cleaving or conventional sawing. Laser sawing is often used.
Type I: The most common type of diamonds. They are characterized by the presence of nitrogen and absorb ultraviolet light from 300 nm. An absorption band is visible in the infrared range. Type I diamonds include Cape and Brown series. Depending on the way nitrogen is distributed in the stone, it may be a Type Ia or Type Ib.
Type II: These diamonds are free of nitrogen. They do not display absorption bands in the infrared range and tend to lack symmetry. They are subdivided in Type IIa and Type IIb. Type IIa stones are usually brown or light brown. All natural blue diamonds are Type IIb, and unlike other diamonds, they conduct electricity.
Sources: ?The Dealer?s Book of Gems & Diamonds? by M. Sevdermish and A. Mashiah, and the American Institute of Diamond Cutting
Aggregate diamonds: Diamonds that have crystallized together with some apparent symmetry. Crystals appear as crosses, triangles, complex shapes or an amorphous mass.
Big sizes: Diamond rough weighing four grains or more.
Browns: The categories of brown-tinged diamonds ranging from finest light brown to good light brown, light-brown, brown and dark brown.
Canary:Golden-yellow diamonds that fluoresce in yellow-orange colors. These are distinct from Cape series yellows, which may fluoresce blue, or not at all.
Cape: Diamonds with colors ranging from the finest whites to yellowish hues.
Cleavages: All diamonds that lack a definite crystalline form, including broken octahedrons and dodecahedrons. Cleavages may be quite large ? the Cullinan is one example.
Cleaving: A process for dividing the diamond rough in two in order to remove impurities before polishing. The cleaver makes a notch, called a kerf, in the stone, then inserts a cleaving knife into the notch and strikes it with a cleaving hammer, causing the stone to split cleanly along a cleaving plane which is inherent in the crystal structure of the stone.
Coated diamonds: Diamonds that are covered by an opaque ?skin.? Polishing a window is often necessary to determine the true color of the diamond.
Collection: The second highest color category for a Cape series diamond, indicating a white stone.
Cube: A six-sided type of rough diamond. Usually these are distorted and have marked surfaces, making them more useful for industrial purposes.
Diamond: An extremely pure form of carbon crystallized into a cubic system. Diamonds sometimes absorb small amounts of other elements, including boron, nitrogen and hydrogen. Diamonds are the hardest substance, rating 10 on the Mohs hardness scale.
Dodecahedron: A diamond crystal that contains 12 facets, formed by resorption of the edges of the octahedron by the kimberlite or lamproite volcanic material. Because they are formed in this manner, their edges are often rounded.
Extra collection: The top category of the Cape series, indicating the finest white colors.
Flat: A common variation in octahedrons in which there are two parallel faces that have developed preferentially so that flat crystals result. Flats vary greatly in thickness. Some can be polished into gem quality diamonds, and some are thin enough to use as watch crystals.
Gem quality: Diamond rough capable of being polished for use in jewelry.
Grain: The measure of the size of rough. Each grain is equal to 0.25-carats, so that four grains equal one carat. Grain is also the term for the direction of the diamond crystal. Determining the grain determines how to cleave or saw the diamond.
Industrial quality: Diamonds that cannot be used in jewelry because of their small size, poor color, deformed or broken crystal shape or complicated crystal structures that cannot be polished.
Kimberlite: A rare kind of igneous rock, one of only two that host primary diamond deposits.
Lamproite: Rarer than kimberlite, this is second kind of mineral that hosts diamonds. The Argyle diamond mine is the best known example of a lamproite diamond deposit.
Macles: Created when one-half of an octahedral twin crystal is rotated 180 degrees in relation to the other half. The result appears like a flat crystal indented along the sides.
Makeable: A diamond crystal that is polished whole, without any sawing or cleaving.
Mesh size: Numerical categories of diamond rough based on a series of sieve plates numbered from 0 to 40, with 40 having the largest holes. For example, stones designated as ?+10? are those too large to sift through the holes of the number ?-10? sieve. Those designated as ?-10? do fall through.
Naat: A junction at which one diamond crystal is embedded inside another diamond crystal.
Octahedron: The most common form of diamond crystal, with eight triangular faces.
Second Cape: The lower end of the Cape series, indicating a stone with more pronounced yellowish coloring.
Shapes: In sorting, the group of rough that includes diamond crystals which are not symmetrical.
Small sizes: Rough weighing less than four grains.
Sorting: The process of separating rough into broad categories and then into more specific subgroups for the purpose of marketing the stones.
Stones: The category of rough that includes octahedrons, cubes and dodecahedrons that are near perfect in form.
Tetrahedron: Diamonds that appear in this form are usually octahedra that have been flattened or distorted.
Triangles: Macles with rounded corners.
Twinned crystals: Diamonds that consist of two or more crystals that appear as a single mass. Most are small octahedrons joined to another octahedron or dodecahedron, or cubes joined together. Because the grain of each component is oriented in a different direction, such stones present a challenge for cleaving or conventional sawing. Laser sawing is often used.
Type I: The most common type of diamonds. They are characterized by the presence of nitrogen and absorb ultraviolet light from 300 nm. An absorption band is visible in the infrared range. Type I diamonds include Cape and Brown series. Depending on the way nitrogen is distributed in the stone, it may be a Type Ia or Type Ib.
Type II: These diamonds are free of nitrogen. They do not display absorption bands in the infrared range and tend to lack symmetry. They are subdivided in Type IIa and Type IIb. Type IIa stones are usually brown or light brown. All natural blue diamonds are Type IIb, and unlike other diamonds, they conduct electricity.
Sources: ?The Dealer?s Book of Gems & Diamonds? by M. Sevdermish and A. Mashiah, and the American Institute of Diamond Cutting