Diamond Glossary

Acidising:

refers to the treatment of diamonds with acids (usually hot) to clean them after mining or after cutting, particularly to remove oxides or polishing residues from surface fissures.

A jour :

is a type of diamond mount that exposes the pavilion to the light and is used in most modern mounts, unlike earlier closed settings.

Baguette:

refers to a diamond cut in the shape of a narrow bar, sometimes tapered at one end. It was named after the long French bread loaf.

Baton:

is another name for a baguette.

Bedrock:

is the solid rock found under deposits of gravels, silt, sand, soil, etcetera.

Bezel facets:

occur when the cross-cutter makes the four top corner facets into eight.

Bicycle tyre:

refers to a thick girdle.

Blocking:

is putting on the 16 main facets by the cross-cutter.

Blue ground:

is the miner's name for the unoxidised kimberlite in a pipe or other kimberlitic deposit.

Blue-white:

is a confusing term often wrongly applied. A blue-white stone should have a faint tinge of blue, even though the description is usually intended to mean colourless. Sometimes it is even applied to stones with a faint tinge of yellow.

Boart:

is a very low-grade diamond suitable only for industrial use. It is also spelt bort, boort, and bortz.

Brillianteerer:

is the skilled person responsible for the final stages of putting on and polishing the 40 facets after the cross-cutter's work. It is also spelled brilliandeer.

Brilliance:

is the intensity of the white light when a diamond is looked at in the face-up position.

Bruting:

is another name for cutting to fashion the girdle outline of a brilliant cut.

Calibré cut:

refers to stones that have been cut to standard dimensions for easy setting into standard mounts.

Carat:

is the standardised unit of weight for gemstones. One carat is equal to 0.20 of a gram.

Clean:

is used to describe a diamond that has no readily visible inclusions, grade SI and above.

Cleavage:

refers to the tendency of a diamond to split along the grain parallel to one of its octahedral faces. It is also a term applied to rough diamonds that have at some time been cleaved from a larger stone.

Cleaver:

is the skilled person who cleaves a diamond into two parts.

Closed culet:

is the sharp point at the bottom of the pavilion of a brilliant cut, or knife edge on an emerald-cut stone.

Cross-cutter:

is the skilled person who grinds and polishes the first 16 facets on a diamond.

Crown:

is the upper part of a polished stone above the girdle.

C.S.O.:

is the Central Selling Organisation which distributes about 80 per cent of the world's rough gem quality diamonds.

Culet:

refers to very small facet on the bottom of the pavilion, parallel to the table. It is also spelled collet and culette.

Cut:

is the shape into which a rough diamond is cut and polished.

Cutter or bruter:

makes the rough diamond round before it is faceted.

Diamond paper:

is another name for the parcel paper.

Diamond parcel paper:

is the specially folded paper in which a diamond is or diamonds are held for carrying, or transporting.

Dispersion:

describes the way a diamond breaks up a ray of white light into colour.

Dop:

refers to the holder used for a diamond that is being polished. A diamond is held in a solder dop by solder and in a mechanical dop by metal jaws.

Extraction:

describes the process of removing diamonds from concentrate.

Extra facet:

is an additional small facet usually applied to remove a small blemish most commonly on or near the girdle.

Extra facet:

is an additional small facet usually applied to remove a small blemish most commonly on or near the girdle.

Faceted girdle:

refers to a girdle on which small facets have been polished to improve the brilliance of the diamond.

Face up:

is the position of a diamond with the table of the stone facing the viewer.

Fancies:

are attractively coloured diamonds.

Fancy:

is a diamond of an attractive colour other than white that is suitable for gem use.

Fire:

refers to the flashing colours seen when a suitably cut diamond is moved, resulting from its dispersion.

Flute:

is a thin paper used to line the inside of a diamond parcel paper.

Full-cut brilliant:

is the correct name for a brilliant-cut diamond with 56 facets plus table and culet.

Girdle:

is a sort of rim at the widest part of a diamond by which it is normally set. It is the resulting circumference of the adjoining crown and pavilion angles at the widest part of the stone.

Girdling:

describes the way a rough diamond is rounded. It is also another name for cutting and bruting.

Grader:

is the skilled person who separates polished diamonds into sizes and quality grades by clarity, colour, and accuracy of cut.

Grain:

is a name used by cutters and polishers to describe the visible evidence of the crystal structure of a diamond, and will usually determine their procedure.

Loose diamond:

is an unmounted, polished diamond.

Loose diamond:

is an unmounted, polished diamond.

Lustre:

refers to the quality of a surface in reflected light. The lustre of a diamond is usually described as admantine lustre.

Mêlée:

are rough stones and shapes under two carats and used loosely for small polished diamonds.

Mixed-cut:

is the mixing of two different cuts for one diamond, such as a brilliant cut crown and step-cut pavilion.

Mount or mounting:

is the part of jewellery into which a stone is set.

Natural:

is part of the natural surface of a rough diamond left on the girdle by the cutter striving for maximum weight retention.

Navette:

is another name for a marquise.

Near-gem:

is a quality of rough diamonds between gem and industrial.

Octagon:

word describes the process of adding the eight main facets to the top and bottom of a stone, which makes its table octagon-shaped.

Open culet:

is a larger than normal culet.

Open table:

is a larger than normal facet.

Open cast or open pit:

describes mining from the surface.

Opening a diamond:

means polishing a window on a rough stone to see inside it.

Pavilion:

is the bottom part of a polished diamond below the girdle.

Pipe:

refers to a roughly funnel-shaped, usually extrusion of volcanic rock that may or may not contain diamonds.

Point:

is the hundredth of a carat, therefore 0.72 carats equal 72 points.

Polished girdle:

refers to a girdle that has been polished but not faceted.

Quality:

measures the degree of excellence of a diamond by its weight, colour, clarity and (polished) its perfection of cut.

Rough:

is the name given to diamonds before they are cut.

Sawyer:

is the skilled person who saw diamonds.

Sawable:

are the rough diamonds that can be divided by sawing.

Scaife:

is also spelled scaive or scaif, and refers to the horizontal turntable or grinding table on which a diamond is polished.

Scintillation:

refers to the flashing and twinkling sparkle of a diamond when it moved under light. A diamond is always more beautiful in motion because its scintillation depends upon the number of facets visible to the eye when the diamond moves.

Set:

is a diamond or other stone set in a mount.

Skin:

is the natural surface of the unpolished diamond.

Sorter:

is the skilled person who separates rough diamonds into sizes and grades of quality by shape, colour, and clarity.

Star facets:

are the eight triangular facets around the table of a diamond that make it star-shaped.

Table:

is the large facet on the top of the diamond's crown.

Treated:

describes a polished diamond that has been altered to change its appearance, eg by artificial colouration, that is, irradiation.

Window:

is the facet polished on a rough diamond in order to see inside it.