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Applying the 4C's to Sapphires and Coloured Gemstones


The 4C's comprise Colour, Clarity, Cut and Carat size. These 4 criteria are measurable to accurately assess, grade and value sapphires and other coloured precious gemstones.


Where I have used the word 'sapphire' in this article, I am also referring to the following precious gems; Apatite, Beryl (Aquamarine, Emerald, Green, Morganite), Chrysoberyl, Garnet (Almandine, Demantoid, Hessonite, Pyrope, Rhodolite, Tsavorite, Spessartite), Iolite, Quartz (Amethyst, Citrine), Spinel, Kunzite, Topaz, Tanzanite, Tourmaline (Indicolite, Chrome, Rubellite), and Zircon.


World of Colour Gemguide
World of Color - Color Communication System

Colour


Colour interpretation can subtly differ from one person to the next, as colours are perceived differently from one person to the next. In addition, other factors, such as time of day, natural lighting and artificial lighting, can impact how colour appears to us.


We can drill down further into Hue, Tone and Saturation to understand colour.


Hue is a sapphire's primary identifying colour, such as yellow, green, blue, purple, pink or red in the case of Ruby. However, hue can also transition between 2 colours, so it can be described as yellow-red, green-yellow, blue-green, purple-blue and pink-red.


Tone is the measure from light to dark - colourless through to black. The most prized sapphires generally have a medium to medium-dark tone.


Saturation measures how pure and intense the colour of a sapphire appears to the eye. Small shifts in saturation can result in sharply increased or decreased values. Describers for saturation include; pale, light, moderate, strong, very dark, deep and the optimal saturation is classed as vivid.


Cushion Cut Emerald with Inclusions
Highly Included Emerald

Clarity


To evaluate the overall clarity of sapphire, we drill down into inclusions, texture and zoning.


Inclusions are the natural markings within a sapphire. Sapphire is evaluated with a x10 loupe and then with the naked eye to determine where the gem sits on the scale. My list includes the clarity description for observing a gemstone with a x10 loupe and with the naked eye.


Internally Flawless or Free from Inclusion - The gem has no inclusion or imperfections when examined with a x10 loupe and with the naked eye.


Very Very Slight (VVS) Clarity or Lightly Included - When examined with a x10 loupe, there are minor inclusions, and when evaluated with the naked eye, these inclusions cannot be seen.


Very Slight (VS) Clarity or Moderately Included - When examined with the naked eye, it appears clean, but minor inclusions can be seen on closer inspection. When examined under a x10 loupe, these inclusions are easy to see.


Slight Inclusions (SI) or Highly Included - The internal markings are apparent when examined with the naked eye.


Inclusions (I) or Excessively Included - When examined with the eye, the internal markings cloud the gem and there may be chips or cracks on the stone's surface.


Colour Zoning in a Sapphire
An Example of Colour Zoning

The texture of sapphire is evaluated by how clear it looks when viewed. Sometimes a gem is heavily included, but those inclusions may be silt or light rutile crystals. These types of inclusion don't always obstruct the general clarity of the gemstone. Occasionally, these internal markings can add to the lustre and internal fire to the gem. The scale of texture is; transparent, faint, moderate, strong and prominent.


Finally, when judging clarity, colour zoning is taken into account. Sapphires can have natural undulation of colour, and this occurrence can impact value depending on its prominence within the gem. An example of colour zoning is a royal blue sapphire that may have some light blue streaks running through it. Colour zoning adds to the uniqueness of sapphire and can undoubtedly enhance its beauty and make it a one-of-a-kind gem. Though it is agreed that top sapphire examples have completely stable colour, don't let zoning discourage you if you love a gem's overall look and aesthetic.


Blue Sapphires in various cuts
Sapphires in various cuts

Cut


Cut is the shape of a gem and the faceting style used to finish the overall piece. When evaluating cut, we also look at the gemstone proportion and quality of its finished polish.


Popular colour gem shapes include; Asscher Cut, Cushion Cut, Emerald Cut, Heart Shape, Marquise Cut, Oval Cut, Pear Shape, Princess Cut, Radiant Cut, Round Cut and Trillion Cut. And then, within the frame of these shapes, different faceting styles are used. A skilled gem cutter will look at the gem and its colour and intuitively facet to a shape and cut that best accentuates the gem's beauty while leaving maximum carat weight. Primary gemstone cutting styles include brilliant cut, mixed cut, step cut and cabochon.


Carat Size


Carat is a measurement value used for diamonds and coloured precious gemstones. As you move up through the carat sizes, prices can steeply increase due to the rarity of larger gems. Generally with coloured gems you can go bigger than you might do with a diamond. The biggest reason for this is coloured gemstones give you better bang for your buck!


The Sapphire Merchant offers an extraordinary range of high end gemstones through to more affordable options to suit any budget. If your perfect gemstone option is not in my online store, contact me today and I will source for you exactly what you are looking for, within your stipulated budget.


Additionally The Sapphire Merchant offers a jewellery manufacturing service.

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