What makes a diamond special? Is it the cut? Or maybe it's the carat size?
The colour and clarity? In fact, it's all of them. All of these qualities work together to create the timeless and treasured pieces we create for you. And all four factors, known as The Four C's, will help you see the difference between a dazzling diamond and a so-so stone. Here's a look at the criteria:
The word carat comes from a natural source: the seeds of a carob tree. Diamonds were traditionally weighed against these seeds until a more scientific and accurate method was employed.
The unit of weight used for diamonds and other gemstones today is the metric carat, which is equal to 0.20 grams. Nearly 142 carats equals one ounce.
Carats are further divided into 100 equal units called points. One hundred points equals one carat, seventy five points equals three quarters of a carat, fifty points equals one half carat etc.
Most diamonds have at least a trace of yellow or brown body colour, however, the colour palette of a diamond is richly varied; diamonds can cover the entire spectrum of colours. Naturally coloured diamonds are rare and are referred to as fancies. These diamonds can come in tints such as green, intense yellow (canary), red, blue, pink, amber and even black. Because of their rarity, fancy colours are held in very high esteem, especially when there is intense colour saturation.
Aside from certain fancies, the most valuable diamonds on the market today are completely colourless stones. In this respect, the diamond is the only gemstone whose colourlessness renders it more valuable.
The most effective way to determine a diamond’s exact colour is to compare it to a diamond which has been colour graded. There are international standards for grading diamonds which have been established to grade the value of a diamond based upon its colour.
At Michael Hill, we use the GIA (Gemological Institute of America) diamond grading system because it is the sytem most widely used and referred to by jewellers all over the world. On the GIA scale, diamond colour grades are indicated from colourless to yellow as D through Z. The top grade colour is called D.
Types of External flaws (blemishes)
Abrasion – Tiny nicks along face edges, producing a fuzzy appearance instead of sharp facet edges
Extra facet – A facet not required by the cutting style, placed without regard for symmertry
Natural – Part of the original crystal surface remaining on a polished stone
Nick – A tiny chip or notch near the girdle or facet edge
Pit – A tiny opening or hole
Scratch – Normally seen as a fine white curved or straight line.
Surface graining– surface indication of structural irregularity. May cross facet junctions as faint lines or cause a grooved or wavy surface
Types of Internal flaws (inclusions)
Bearding – Tiny feathers extending from a rounded girdle
Chip – Often a small hole or shallow opening, usually on the girdle edge
Cloud– A hazy or milky area made up of a number of very small inclusions, usually pinpoints; sometimes needles.
Feather – A separation or break due either to cleavage2 or fracture3, often white and feathery in appearance.
‘Carbon’ Spots or Pinpoints – Specks appearing to be black are typically tiny cracks or crystals
Internal Graining – Internal growth lines which indicate irregular crystal growth; may appear milky, like faint lines or streaks, or may be coloured or reflected.
Pinpoint – A very small inclusion which under 10x magnification, appears as a dot, either singly or in groups of strings.
The GIA clarity grading system assigns clarity ‘codes’ ranging from F to I-3. These codes are defined and described below.
F / IF – Flawless / Internally Flawless
Diamonds in this category have no internal or external imperfections. IF diamonds may have some minor surface blemishes.
These rare diamonds must be free of internal imperfections when examined by a qualified diamond grader using 10x magnification.
VVS – Very Very Slightly Included
Diamonds in this category may have a very tiny pinpoint of carbon, cloud, gas bubble, polishing line or faint knot line, faintly visible only through the pavilion and small and shallow enough to be removed by minor repolishing. These inclusions are difficult for even a skilled grader to locate under 10x magnification.
VS - Very Slightly Included
May have some inclusions that are more easily visible under a 10x magnification. A bubble or included crystal or other small blemish may be seen through the crown.
SI – Slightly Included
These diamonds contain larger inclusions that may still not be visible face up to the naked eye but visible under 10x magnification.
I – Imperfect
Refers to diamonds with inclusions that are visible to the naked eye.
The term cut is sometimes confusing because it has a variety of meanings. Generally, cut refers to
After careful examination of the rough stone, the cutter decides on a final shape for the diamond. Their decision is influenced by several factors such as the original shape of the stone, its dimensions, inclusions and the inevitable loss of weight during cutting.
It is the cut that enables a diamond to make the best use of light. When a diamond is cut to good proportions, light is reflected from one facet to another and then dispersed through the top of the stone. If the cut of the diamond is too deep, some light escapes through the opposite side of the pavilion. If the cut is too shallow, light escapes through the pavilion before it can be reflected.