A Guide to Gemstones

Gemstone (Coloured stone) certification
Gemstone certification is much more complex than with Diamond certificates and most people wouldn't even know that a coloured stone would be able to have a certificate. The locality of a coloured stone can greatly affect the price of the stone. Many people do not realise that most coloured stones on the market have had some kind of treatment applied to the stone to enhance its beauty. Gemstones have been treated/enhanced for hundreds of years to help with the durability, colour and clarity of the stone. Some of the treatments used are heating, irradiation, diffusion treatment and oiling. 

Gemstone stone reports will identify the following:

  • The type of gemstone,
  • Whether the stone is natural or synthetic,
  • The stones origin geographically,
  • If the stone has had any form of treatment.

It will also include details such as carat weights, the shape, cut, measurements and sometimes a photograph of the item/gemstone.


Gem and Pearl Lab

The Gem and Pearl Laboratory Limited was founded in 2003. Stephen Kennedy is a gemologist with experience of laboratory-based pearl and gem identification dating back to 1980.

Within the UK the Gem and Pearl Laboratory offers:

  • Nationally recognized reports for coloured gemstones and pearls,
  • Heat treatment and country of origin opinions for ruby, sapphire and emerald,
  • Unparalleled practical knowledge of pearl identification,
  • Authoritative advice on the application of gem and pearl descriptions within jewellery.

Interested in the history of various gemstones click below to read about your favourite stone.

The word ‘Ruby’ comes from the Latin word Rubeus meaning red. Rubies and Sapphires are at times mined at the same location but they have different formations. Rubies are formed in marble and Sapphires are formed in granitic pegmatites. Rubies are a variety of the mineral corundum. The red dominant colour of a Ruby is created by having evidence of chromium in the stone as a substitute for the ion in a corundum structure.The most valuable shade of red for a Ruby is known as ‘Pigeon-blood red’. In natural Rubies you will find inclusions of ‘rutiles’ which are natural needles known as silk.

Ruby is the birthstone for July.

The word Sapphire comes from the Latin word ‘Sapphiru’ meaning blue. Sapphires are mined from loose soil or sediments that have eroded and then been rearranged by water and deposited outside of a marine environment. Sapphires come in a variety of colours. Blue is the most popular colour but they can also be found in yellow, pink and green. The most well known countries where Sapphires are mined are Burma, Sri Lanka, Australia and India. Depending on the geographical location Sapphires vary in appearances. The colour of a Sapphire is called the hue, the brightness is described as the variance of saturation and the tone is a range from light to dark. Sapphires that have not been treated are the rarest and as will be more expensive and the most valuable. The Origin of the sapphire will also have an impact on the price.

Sapphire is the birthstone for September.

Peridot is a semi-precious Gemstone, also sometimes called ‘Chrysolite.’ The name Peridot comes from the Arabic word ‘faridat’ which means ‘gem’. A Peridot is most recognisable for its striking bright green tones. Iron makes the gemstone green, although this gemstone does come in other colours such as a yellow-green to brownish green. However, the most valuable Peridot is a deep lime green with no other tones. Peridots are made from the mineral Olivine. Peridots have a fascinating history dating back over 4,000 years and most are formed deep inside the earth and brought up to the surface by volcanoes where they are then found in extrusive igneous rocks. Some Peridots come to Earth in meteorites, however this is very rare. A slice of meteorite with Peridot crystals was founded in Argentina in 1951.The first known use for Peridot was used in jewellery over 3,500 years ago by the Egyptians. Today the gemstone is a very popular choice in jewellery perhaps because of it’s striking colour and that it is 6.5 to 7 on the Moh scale meaning it's reasonably strong. Traditionally Peridots symbolize 16 years of marriage, however they are also given as an alternative for the 1st wedding anniversary. Peridots are believed to be rich with healing energies and spiritual connotations

Peridot is the birthstone of August

The word ‘Opal’ is believed to come from the ancient Rome word Opalus meaning precious stone. Opals were mainly sourced in Australia, but they can now also be found in countries like Brazil and Mexico. The Opal is a hydrated amorphous form of silica and because of its amorphous character it comes under the category mineraloid. Although the Opal is a mineraloid it has an internal structure made up of silica spheres in a hexagonal or cubic lattice.The internal structure of the Opal diffracts light, allowing the play of colour to be seen. A ‘play of colour’ is the terminology that describes the unique and vibrant colours of the Opals. The unique play of colour to be found in Opals tends to be a combination of red, orange, yellow, blue and green. Black Opals are considered to be the rarest and these Opals tend to have a darker play of colour. Historically, in the Middle Ages, the Opal was thought to provide good luck because it was believed the gemstone combined all of the qualities of every other gemstone whose colours were found within it. In 2008, it is believed that NASA discovered Opal deposits on Mars.

Opals are the birthstone for October.

Garnets are a large group of rock forming minerals that have been used since the Bronze age as Gemstones and abrasives. All Garnets have similar physical properties and crystal forms but differ in chemical composition. The different species are Pyrope, Almandine, Spessartite, Grossularite, Uvarovite and Andradite, however in addition to these there are several other Garnet varieties. Altogether there are at least 17 different varieties of Garnet. Garnets are found in Metamorphic and Igneous rocks. They form under high temperatures and pressure and are found mainly in Africa, India, Russia, South America, Madagascar, Pakistan, and the US. Thousands of years ago, red Garnet Necklaces were worn by Egypt’s Pharaohs. They were entombed with their mummified bodies as valuable goods for the afterlife. Garnets are mostly known for being red, and these are the most common, however, they actually come in almost every colour including green, yellow, blue, pink, orange, brown and even purple! Green, orange and purple are rarer and are, therefore, more valuable. Garnets are a relatively hard mineral, they range between 6.5 and 7.5 on the Mohs scale, which makes this Gemstone a popular choice when choosing jewellery as it's very wearable.

Garnets are the birthstone of January

Tourmaline is a unique mineral and is known for being a semi-precious gemstone. It is a large group of crystalline boron silicate minerals with other elements such as aluminium, iron, magnesium, lithium and potassium. The wide range of compositions and colour zoning within crystals causes Tourmalines to occur in more colours and colour combinations than any other mineral group. Tourmalines are very well known for their different and unique colours and come in various colours including blue, green, orange, pink, purple, red, yellow, brown, black and even colourless. The Green Tourmaline is the most common. The first ever recorded Tourmaline was a green crystal discovered in 1554 by a Spanish explorer who believed it was an Emerald. For many years people have confused Tourmaline with other gemstones, such as Emeralds and Rubies. In the 1800’s a scientist recognized Tourmalines as minerals and today it is a very popular and well known gemstone. Some believe that Tourmalines strengthen the immune system and provide positive thoughts. Tourmaline is 7 to 7.5 on the Mohs scale, so it is a tough and durable gemstone.

The Emerald is the most valuable gemstone within the beryl family. The oldest Emeralds are believed to be 2.97 billion years old. They are known as the "stone of successful love", it is believed to open up the nurtures of the heart and provide healing, bringing vitality to the spirit. The incredible green colour this stone shows is formed when chromium, vanadium and iron are present in the beryl mineral. Varying degrees of each element gives the range of colour. Iron gives the stone it's bluish tint, Chromium and vanadium create the intense green colour. To be considered a genuine Emerald the stone has to have a distinct colour which should range from bluish green-green- yellowish green. If it is not a rich saturation of colour it would be classed as a green beryl instead of an emerald. Columbian Emeralds get their colour primarily from the element chromium Brazilian Emeralds mainly from vanadium Zambian Emeralds mainly from iron

Emerald is the birthstone of May

Aquamarines colour ranges from greenish blue to blue, the more blue in colour the more desirable the stone is. Aquamarines are part of the Beryl family (The same family as Emerald and Morganite). They are different from Emeralds as they have fewer fractures and inclusions and are usually clear to the naked eye. Aquamarines are associated with keeping a cool temper, the calming pale blue colour has long been compared to the sea, in fact its name is derived from the Latin words Aqua-Water and Marina-Sea. It is also a symbol of youth, good health and hope. The colour is usually improved by heating.

Aquamarine is the birthstone of March