Cut has two meanings in the diamond and jewellery business and can be a little confusing.
The first meaning relates to the shape and style of a polished diamond, such as Round brilliant and Emerald cut. See diamond shapes.
The second meaning (in reference to the 4C's) is used to describe the relative quality of the proportions and finish of a polished diamond which is what will be explained briefly in the following paragraphs. In the trade this is normally referred to as Make. Finish refers to the quality of a diamonds polish, the condition of its girdle and the precision of the faceting.
The cut or make of a diamond is the most important of the 4C's. This is a very complex subject and is an on-going study by the major diamond grading laboratories. Make is the only one of the 4C's that man, the diamond cutter, can control. Polished diamonds should be considered optical instruments and ideally all light entering a diamond should be internally reflected back to the observer.
The diamond cutter should analyse a rough diamond to determine how to extract the most beauty out of that rough diamond. In a commercial environment they also cut a diamond to retain the most weight and therefore perceived increased value, to the uninitiated. This retained weight will be to the detriment of a diamonds face-up appearance and will be displayed as either very lumpy (small diameter) or very spread (wide diameter). This ties in with the minimum diameters that you should demand when purchasing round brilliants. See carat weight.
|Diamonds cut with Excellent to Good proportions allow a maximum amount of light to be returned to the observer and thus have more brilliance and fire.||A diamond with a deep pavilion will appear dark in the centre of the diamond due to light leakage from the pavilion. Diamonds with a make grading of Medium to Poor will appear like this.||A spread fisheye diamond with a shallow pavilion creates a white circle at the edge of the table when looking down on the diamond. This is actually the reflection of the girdle at the edge of the table. Diamonds with a make grading of Medium to Poor will appear like this.|
With the advent of new technology, polished diamonds can be measured very accurately and quickly using laser imaging technology. These measurements are the physical dimensions of the diamond and include all mm, percentages and angles of the diamond that are listed on the majority of diamond grading reports.
As stated previously there are no universally accepted make parameters for round or fancy cut diamonds.
The GIA make parameters for rounds are now becoming the world standard, although all diamond grading laboratories have their own versions of what they consider to be the best and worst make parameters.
All round diamond make parameters on the diamonds.co.nz database are graded using the GIA Facetware program and are measured using laser imaging technology. Further Information on the GIA Facetware program can be found at www.gia.edu
Rounds on diamonds.co.nz are classified as Excellent, Very Good, Good, Fair and Poor
Fancy cuts are a very complex issue and diamonds.co.nz now uses the Accredited Gem Appraiser system developed by David Atlas to differentiate and identify the make of Princess, Radiant, Emerald, Marquise, Oval and Pear shape diamonds listed on the database. More information can be found at www.gemappraisers.com
diamonds.co.nz endeavours to purchase fancy shapes of the best make possible with an emphasis on symmetry and polish.
Fancy shapes on diamonds.co.nz are classified as Ideal, Premium, Fine, Average and Poor.
Ideal and Premium are very strict grades and as with Excellent in rounds. Average is a good commercial make. Sometimes diamonds can be listed with a Poor make on the database. The main reason is because of very thin girdles – this can push a diamond into Poor while the rest of the parameters are in the Ideal to Fine range.
Please click here to view a chart outling the make parameters used to allocate the above make grades for diamonds.co.nz fancy shape diamonds.
Please note that the GIA does not allocate make grades to any fancy shapes – they list Polish and Symmetry grades only. Gem Appraisers are not connected to GIA in any way.
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