THE GIA Diamond Grading Terminology is:-
A diamond’s cost is based on the characteristics known as the “4 C’s”. CUT, COLOUR ,CLARITY AND CARAT are the quality elements which together with the Carat Weight determining the value of a stone. The closer a diamond grades to the benchmark for each of these scales, the rarer and the more costly it will be.
The Cut has a profound effect on the visual appearance of a diamond and gives it the fire and sparkle.
The transformation from a rough diamond to the end product is due to the cut. The cut mainly comprises proportions of the facet angles, how each facet is symmetrical to each other, the polish and finish of the diamond also play a huge role in the cut of a diamond. Cut is determined as Excellent, Very Good, Good, Fair and Poor depending on the above mentioned factors as well as light that gets reflected out of the diamond.
The facets play an important role in determining the cut to be superior. In a standard round brilliant cut, there are 57 or 58 facets, depending on whether there is a culet or not, the diamond is divided into the crown and pavilion by a line across the circumference of the diamond called a girdle.
Above the girdle are the table, eight bezel facets, eight star facets and sixteen upper girdle facets that comprises the crown facets. There are eight pavilion mains and sixteen lower girdle facets and a culet if present in the pavilion.
The most widely and expensive cut today is the round brilliant cut. Another cut used is the emerald cut, mainly baguettes and tapered baguettes are of this cut. Other cuts over the years that have been used are single cut, table cut, rose cut, old mine cut and many others.
Very often cut is confused with Shape, Shape is the appearance of a diamond. The common shapes used in diamonds are round brilliant, princess, marquise, pear, heart, oval, emerald cut, etc.
By definition, 1 carat is 200 milligram.
Since most diamonds sold in the market weight less than 1 carat, the carat is usually subdivided into points. There are 100 points in 1 carat, so that a diamond weighing 3/4 carat would be a 75 point diamond.
1 carat = 200 milligrams = 100 points.
Please note that carat weight is not a factor which denotes diamond quality. It merely denotes the size of a diamond, by its weight.
Diamonds of 0.50 - 0.75 carat are very popular for their combination of size and value.
Diamonds above 0.20 carat are known as solitaire diamonds.Large diamonds are rarer to find in mines than smaller ones, which makes large diamonds more valuable.
Carat is the unit of weight for all gemstones. One carat is subdivided into 100 “points”. Therefore a diamond measuring 75 points is 3/4 carat in weight, or 0.75ct. (There are five carats in a gram. )
Colour You have a choice in quality between pure flawless and approximately 9 grades of quality below that the top level, the top ones being the most beautiful stones.
D : Absolutely Colourless. The highest colour grade, which is extremely rare.
E : Colourless. Only minute traces of colour can be detected by an expert gemmologist. A rare diamond.
F : Colourless. Slight colour detected by an expert gemmologist, but still considered a "colourless" grade. A high quality diamond.
G - H : Near colourless. Colour noticeable when compared to diamonds of better grades, but theses grades offer excellent value.
I -J - K : Near colourless. Colour slightly detectable. An excellent value
L - M : Noticeable colour.
N - Z : Easily noticeable colour.
The ideal diamond is completely colourless, and the most expensive. However most diamonds which appear colourless actually have slight tones of yellow or brown. SGL, grades colour alphabetically from D (totally colourless) to Z (heavily tinted).
Please note the difference in grades are subtle, and mostly not visible to the naked eye. A diamond with a visible tint such as K and above can still be beautiful if it has good clarity and cut. Only diamond graded N onwards have a tint visible to the naked eye. From S onwards, the tint grows more intense. Natural colour diamonds come in all shades and colour of the rainbow. The most popular colour are combination of pink, blue, brown, yellow, orange, green and red. Yellow is the most common naturally occurring fancy colour, white, red, blue, and green diamonds are very rare.
Increasing degrees of colour are measured on a scale ranging from no colour at all, the traditional diamond (D) to deeply coloured (Z).
Beyond “Z” is the range where the diamond’s colour is , called “fancy colours”. Diamonds of known colour are used as comparison stones for colour grading.
Clarity is measured on a scale ranging from pure (flawless) to heavily included
A diamond’s clarity is determined by internal characteristics called “inclusions” and surface features called “blemishes”. These irregularities are naturally occurring and were created in the liquid magma (volcanic rock) within which the diamond was formed.
This chart refers to the scale of inclusions, the fewer there are the better the stone is.
An example of a commissioned set of rings created in 18ct white gold and set with gvs quality diamonds.
a Helen Burrell 'wave ring' design.
THE GIA DIAMOND CLARITY SCALE says that the grades are defined by these descriptions:-
Characteristics within the diamond or on the surface define the clarity of a diamond. Characteristics that are within the diamond are known as inclusions and those that are external to the diamond are known as blemishes. Clarity ranges from Flawless to I3.
FL : Completely Flawless.
IF : Internally Flawless - external flaws can be removed by further polishing.
VVS1- VVS2 : Very Very Slightly Included - only an expert can detect flaws with a 10X microscope. By definition, if an expert can see a flaw from the top of the diamond, it is a VVS2. IF the expert can only detect flaws while viewing the bottom of the stone, then it is a VVS1. Please Note : VVS1 clarity diamonds do not have any internal black marks.
VS1 - VS2 : Very Slightly Included - you can see the flaws with a 10X microscope, but it is not obvious (takes more than about 10 seconds to identify the laws).
SI1 - SI2 : Slighty Included - you can see flaws readily with a 10X microscope.
I1 - I3 : Included - you can see flaws with the naked eyes. Eminently visible.
(I would not normally recommend using these lower grades.)
Inclusions seen within a diamond vary from diamond to diamond, No two diamonds will ever be the same. Each diamonds characteristics are unique.
Size is the most visible factor that determines the value of a diamond. The price of the diamond rises exponentially according to its size.
'As you can see from this Information, the quality level for the stone has an impact on the price you would pay for it, but will also, because of the various grades, give you room to adjust the choice of stone to fit your budget.
If for instance you want to keep to a particular size of stone such as a full or half carat , There will be the various qualities at different price levels to choose from in those sizes.
Another white stone to consider is white sapphire, which is beautiful but has slightly less fire to it.
This offers you the choice of a very good price in terms of a comparable sized diamond.
Please make sure your partner would be happy with this idea, as it could be they would prefer a small diamond of a high quality rather than a larger sapphire.'