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Precious Stones in Jewellery.

A list of simple facts and answers to many questions about diamonds, emeralds sapphires and rubies. Other stones can be found in our semi-precious stones section or learn about birthstones.

Diamonds 2ct Brilliant cut diamond with baguette shoulders formed over 50 miles below the surface, the hardest and most prized mineral on Earth

What does the GIA certificate look like?

Selected according to the "Four C's" principle of Cut, Colour, Clarity & Carat.

Cut has many variations but most common are brilliant, baguette, princess and emerald cuts. Click here to see all the variations. A good diamond cutter will chose the cut to maximise brilliance or reflected light. The rear facets of the stone provide this reflection and must be cut at an angle of not less than 24.5 degrees or light is not reflected back to the eyes of an observer.

Colour is determined on a scale from D (clear) to Z (light yellow or brownish tinting). Click on the GIA thumbnail to see this scale. Colourless diamonds are the most sought after as they return the most light.

Clarity runs on a scale from FL (flawless) through IFL (internally flawless), VVS1 (very, very small inclusion), VVS2, VS1..SI...all the way to I3. The clearest stones have the fewest inclusions and so absorb the least light - making them more radiant. Click here or on the GIA thumbnail to see this scale

Carats are the standard unit of weight originally measured against carob tree seeds, they are set at 0.2 grams per carat. One carat is 100 points, so 30 points equals 0.30 carats. Click here to learn more about stone size verses weight.
Emeralds Oval emerald & diamond cluster a variety of the mineral Beryl, found in dark shales and limestones

Emeralds are the softest of precious stones and this has led some to (mistakenly) believe that emeralds are unlucky. This is NOT the case. They do require more careful ownership than the other tougher stones, but if set correctly they should not warrant much extra concern. Click here to see all the cutting variations.Some of the best emeralds come from Columbia.

Carats: Larger stones cost more per-carat thanks to rarity of bigger top quality emeralds. Sub-1/2 carat stones are sold by the millimeter, not by carat

Clarity: There are many types of acceptable flaws in emeralds, BUT cracks or "feathers" deep into the stone will endanger its durability and "colour-zoning" will mar the purity and uniformity of colour. These should be avoided. There can also be man-made "liquid inclusions" that are holes inside the stone filled in with fluid - acceptable if they don’t generate a milky appearance.

Transparency: You are looking for a gem through which light passes easily without turning cloudy, milky or hazy



Sapphires Sapphire ring a variety of Corundum made blue by iron & titanium oxides

There is a huge variety of colour for these stones, no particular shade being more desirable than another. Avoid shades of grey or black in blue stones. The good lighter coloured stones are from Ceylon ( Sri Lanka) while the darker stones come from Burma (Mayanmar). Click here to see all the variations.

Colours other than blue are known as fancy sapphires. In order of value: Padparadscha (a beautiful pinkish-orange); Pink (some may be sold as rubies in error); Orange (medium-dark red-orange); Purple; Yellow (vivid light-yellow); Green. All are beautiful and your choice is purely a matter of personal preference.

Carats: Sapphires are denser than diamonds, so a one carat sapphire could be considerably smaller than a one carat diamond

Clarity: It is important that the stone has a uniform colour spread and doesn't appear in irregular pockets a "flawless" sapphire is a fake. Cracks (feathers) in the stone from the surface can seriously weaken it while internal inclusions might block consistency of color or transparency. The lighter the colour, the more free from flaws the stone should be. Flaws are acceptable if they don’t threaten durability or adversely affect color. The GIA scale works down from the top quality VVS (very, very slightly included) to Dcl (declasse).

Rubies Ruby with step-down diamonds a variety of Corundum made red by chromium

Once again a variety of colours. The pinker stones are very popular while the darker "pigeon's blood" rubies are much sought after. The best come from the Mogok region of Burma. Click here to see all the variations.

Carats: like sapphires, rubies are denser than diamonds, so a one carat stone will be smaller than a one carat diamond The important factors in choosing Rubies are all colour related

Hue : Pure "traffic-light" red is the impossible dream, but a good comparison point

Tone: lightness/darkness or hints of white, black, brown and grey with consistency of tone throughout the stone. Darker stones are generally more valuable.

Purity or Intensity: The GIA scale for judging purity runs through Vivid; Moderately strong; Very Slightly Brownish or Greyish; Slightly Brownish or Greyish; Brownish or Greyish.

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