The Diamond Certification Laboratory of Australia (DCLA)

Distance in millimeters or percentage from the table plane to the culet. Also known as ‘total depth’ or ‘total height’.

Total depth expressed as a percentage of the diameter.

Diameter is a reference measurement against which most of the proportions on a diamond are calculated. On a round brilliant cut diamond, this is the length in millimeters of a straight line going through the center of a diamond. Click here to learn which standard diameter measurements correspond to specific well-proportioned carat weights. On a fancy shaped diamond, this is the average measurement in millimeters of the length and width.

Mineral composed almost exclusively of crystallised carbon. Carbon, when subjected to extremely high temperature and pressure, changes form and crystallises into diamond. Only approximately 20% of natural mined diamonds are of gem quality; the remaining 80% are industrial grade diamonds.

Organisation of diamond industry members. The main purpose of a diamond bourse is to provide an environment for the trading of diamonds within a set of ethical business practices. All diamond bourses have a legal, ethical framework to enact regulations for members and protect consumer confidence. Also referred to as a ‘Diamond Club’.

Diamond bourse, or organisation of diamond industry members. The main purpose of the DDCSA is to provide an environment for the trading of diamonds within a set of trading practices. The DDCSA has a legal, ethical framework to enact regulations for members and protect consumer confidence.

Minute particles of diamond, usually used as a high-quality abrasive for diamond polishing or industrial grinding, sawing, and filing.

Tool used to manually measure the dimensions of a diamond.

The bonds between carbon atoms that make up a diamond are stronger in some planes than others; this means that diamonds are marginally harder at some angles than at others. Diamonds thus have certain planes of weakness along which they can fracture, split or break. Directional hardness is related to the toughness and durability of diamonds.

Visible play of colours created by the break-up of light in a diamond. When light enters a diamond, it refracts then reflects off of the pavilion facets and separates into a rainbow of colours as it shines out of the crown facets. Also known as fire.

Overall resistance to wear and damage, considering both hardness and toughness. Diamonds are the hardest gemstone on earth, but are not the toughest – they have directional hardness.