Diamond Glossary

Aggregation- The generic term used by the DTC to refer to the process of blending (rolling together), like for like, rough diamonds from different countries that have already been accurately sorted and valued. The diamonds are then split into boxes for sale to the DTC's Sightholders.

BBBEE company- Broad Based Black Economic Empowerment program- Is an economic policy initiated by the South African government aimed at providing prioritised economic developement opportunites for previously disadvantaged groupings in the mainstream economy.


Carat- A unit of mass for diamonds and gemstones; it has varied over time and from place to place, and was standardised worldwide in the 20th century at exactly one-fifth of a gram (the metric carat).  One of the 4Cs.


C.A.R.P- Completely Automated Recovery Plant.


Crown- The upper part of a polished diamond.


Culet- 1)   The facet at the point of the pavilion on a polished stone (if present).

             2)   The pavilion point itself (if the facet is absent).

             3)   The general region of the pavilion point.


Dense Medium Separation- Diamonds are heavier than the material that surrounds them. Once the ore has been crushed to a manageable size, we mix it with a slurry made of finely ground ferrosilicon prepared to a specified density. In a method known as Dense Medium Separation (DMS) that exploits the relative densities of different materials, we apply centrifugal force to the mixture to separate a diamond-rich concentrate.


Diamantaires- The French term ‘diamantaire’ (‘diamantair’ in Flemish) is used in the diamond industry, to denote a person that possesses diamond-related skills.


Girdle- The edge of a diamond, at the widest part. It can be polished, faceted or bruted.


Grainers- 1)  Normally refers to smaller stones whose weight is expressed in grains rather than carats (particularly rough stones weighing less than 2.79¢ and polished stones weighing less than 1¢).

2)   In the DTC, ‘grainers’ refers to stones weighing more than 3gr but less than 2.79ct.  Stones that are smaller than this are sometimes colloquially referred to as ‘smalls’ within the DTC. 


Inclusions- Any naturally-occurring material inside a diamond (including internal cavities and cracks).


Indicator minerals- Minerals that are used to help locate diamond deposits.  They are minerals which are characteristic to kimberlite, but which are usually more abundant than diamonds (and therefore easier to find).  Indicators form in association with diamonds in the kimberlite and are scattered over a wide area by erosion.  Therefore, by tracing these indicators, the source of the kimberlite may also be found. 


Kimberlite- An intrusive igneous rock that is sometimes diamondiferous.  It is unevenly grained, containing minerals such as olivine, phlogopite, pyrope garnet, cemented with a groundmass consisting of minerals such as serpentine, calcite and chromate.


Loupes- A magnifying glass, usually magnifying 10 times (10x).  A ‘hand-loupe’ is hand-held, whereas a ‘headloupe’ has two lenses (one for each eye, providing stereoscopic vision) mounted on a frame that is worn on the head.  For practical reasons, the standard magnification for a diamond-sorter’s headloupe is 3.5x rather than 10x.


Near gem quality- A quality band between gem and industrial.


Open-pit mine-  Mining from the surface by removing overburden to expose the ore below.


Pavilion- The lower part of a polished gem, below the girdle.


Sightholders- The DTC’s clients.  Because the DTC does not have enough supply to meet demand, and does not require its purchasers to compete on price for reasons of commercial stability, it must use objective criteria (see Supplier of Choice) in order to select its customers, who are known as Sightholders.


Simulants- A substance used to imitate diamond.


Smalls- Colloquial term for stones weighing under 3gr.


Supplier of Choice- A corporate strategy to encourage the development of efficient channels of distribution which drive consumer demand for diamond jewellery, delivering new and innovative products to the consumer and meeting the needs of  international standards of Best Practice.


Synthetic- A man-made reproduction of diamond that has essentially the same chemical composition, crystal structure and physical properties as its natural counterpart (the term ‘diamond’ is a scientifically-recognised mineral term, not a brand name, and properly refers only to stones formed by natural geological processes).


Table- The largest, central, octagonal facet on the crown of a polished diamond.


Treatment- Any non-natural processes (other than shaping, polishing and surface cleaning) that change, interfere with and/or contaminate the natural appearance, composition or durability of a gemstone.  For diamonds, this includes (but is not limited to) colour treatments (anddecolourisation or ’bleaching’), fracture-filling, laser-drilling, irradiation treatment, and coating.


VCT Programmes- Voluntary HIV/AIDS counselling and testing programmes.