Independent centre of excellence

Gemstone Guides



Your guide to Gemstones

AnchorCert Gem Lab offers:

  • Identification of any cut gemstone
  • Identification of treatments e.g. heat treatments, glassy residues, fissure filling, cobalt coating
  • Determination of country of origin on certain gemstones

Verbal consultations or written reports are available. Gemstones are required loose for testing but can sometimes be tested within their mount. Please contact AnchorCert  Gem Lab with your requirements.

Emerald Factsemerald

  • Emeralds are colour varieties of the mineral Beryl.
  • The name Emerald derives from a Persian word meaning “green gem.”
  • Emerald is the birthstone for May.
  • Hardness of  7.5 on the Mohs' scale. Although Emerald is quite hard it is not very tough and can be chipped from impact.
  • The majority of Emeralds are mined in Colombia, Brazil Pakistan and Russia.
  • Emeralds green colour is due to the presence of chromium and +/- vanadium
  • It is common for a lot of Emeralds to be oiled, meaning that they are immersed in oil which fills the many cracks and fissures to which Emeralds are prone.
  • Oiling can sometimes improve the colour of an Emerald by using green coloured oil. It is advisable to have an Emerald re-oiled after several years.
  • Emeralds should never be cleaned with steam or any cleaning solution that contains petroleum distillates or any other organic solvent. They should not be placed in ultrasonic cleaning equipment and should not be exposed to high heat. An Emerald should be cleaned gently with a warm, mild detergent solution and a very soft brush, such as a worn-out toothbrush.

Ruby Facts

  • ruby stoneRuby is the red variety of the Corundum family.
  • Ruby derives from the Latin word for red, rubeus.
  • Corundums have a hardness of 9 on the Mohs' scale. No other gem is harder than a Corundum except Diamond.
  • Ruby is the birthstone for July.
  • It is rare to find a large ruby without inclusions.
  • The better quality rubies are found in Burma, Vietnam, Tanzania, Kenya, Thailand, and Cambodia. But can also be found in Colombia, Afghanistan, Pakistan, India and in the U.S.A.
  • Rubies are often heated to improve their colour and occasionally, open fractures and cavities are filled with glass to give a cleaner appearance.
  • If cut into cabochons (smooth domes) a star with six rays can appear on the stone. 
  • There are no internationally accepted standards for the colour of a ruby, so the cut-off between ruby and pink sapphire is not always so straightforward.

Sapphire Factssapphires

  • Sapphires are members of the Corundum family of minerals.
  • This gemstone has a hardness of 9 on the Mohs' scale.
  • Available in a variety of beautiful colours including blue, yellow, colourless, black, white, orange, pink and brown with the most popular colour being cornflower blue.
  • Sapphire is the birthstone for September.
  • It is the presence of trace elements like chromium, iron, vanadium and titanium which are responsible for the wide range of colours. A variety of orangish-pink sapphire is called padparadsha, which means “lotus flower.”  
  • Heat treatment is commonly used to deepen sapphire colour and improve clarity.
  • When cut into cabochons, sapphires produce a star with six rays which stretch across the stones surface.
  • Sapphires principal sources are Africa, Burma, Sri Lanka, Thailand, Australia, India and Brazil.



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