They are categorized and valued based on their size, quality and rarity.
In addition to these minerals there are other organic materials, such as amber or lapis lazuli, which are often classed as gemstones due to their colour and use in decorative jewellery throughout history.
The study of gemstones is called ‘gemology’ and is carried out by ‘gemologists’.
They can be classified into different groups, species, and varieties by examination of their chemical composition and the form they are discovered in.
Gemstones can be collected on their own or as part of a wider jewellery collection.
Gemstones may be collected because of their monetary worth or because of their aesthetic value.
In the traditional classification of gemstones they can be split into two separate groups: precious and semi-precious stones.
This classification has no technical basis in scientific fact, but originates from systems first used in Ancient Greece.
They were judged on their rarity at the time, combined with their hardness and quality of colour. Using this classification diamonds, rubies, sapphires and emeralds are considered precious stones.
All others are considered semi-precious.
This method, however, is not always indicative of a gemstone’s actual value and most jewellers and gem experts no longer use this classification. But in terms of public perception, the reputation of these four ‘precious’ gemstones still places them above all others.
Gemstones are primarily valued on their clarity, colour, number of carats and cut.
Their clarity is based on the number of flaws in the stone, known as inclusions.
The colour is judged on its purity, along with any unusual optical phenomena it may display such as colour zoning, and asteria.
The number of carats is a measurement of gemstone size, with a carat being a unit of mass equal to 200mg.
The cut of a gemstone relates to the manner in which it has been shaped and polished from its natural state.
Diamonds are rated first and foremost on their cut, whereas other coloured gemstones are rated on their colour.
Diamonds are cut to specific mathematic guidelines of angles and length ratios in order to reflect the most light. These cuts are created using a faceting machine to create the series of small flat angular surfaces on a diamond called facets.
Many other gemstones are cut as smooth, dome shaped stones called cabochons.
Early uses of gemstones
The first gemstones ever cut and used by humans were cabochons cut from soft, naturally occurring materials such as amber, lapis lazuli, jade and turquoise.
Stones were shaped by rubbing them with other stones, then polished using 'sand' as an abrasive.
Some of the earliest examples have been discovered in Ancient Egyptian tombs, with intricately carved cabochon cuts, known as "Glyptic" gem carvings, dating back to the 7th millennium B.C.
These early beads were used as currency before the first coins were used around 600 B.C. Beads were also used in talismans and amulets and to express power and wealth, particularly in Ancient Egyptian culture. They were also used on personal seals and signet rings, and impressed into wax to create signatures.
During this time early Chinese civilisations had already begun to mine Jade, which they considered the ‘Imperial gem’. It was used for ceremonial items, decorative objects and even royal burial suits, and to this day is valued in Chinese culture as high as diamonds and gold are in Western cultures.
Historians believe that diamonds were discovered in India during the 4th century B.C., and India was one of the first countries to mine the gem.
The most famous Indian diamonds are the Golconda diamonds, originating in an area between the lower reaches of the Godavari, Wainganga, Wardha and Krishna-Venva rivers in central India.
The mines around the area became legendary and the name ‘Golconda’ has become synonymous with enormous wealth. Amongst the famous diamonds to have originated from this area include the Hope Diamond and the Koh-i-noor Diamond.
These diamonds were transported across land through Persia to Europe, and by the 14th century the majory of all European diamonds had originated in the Indian mines. However, the land journey was deemed so long and perilous that it led explorers to search for another option.
In 1488 Bartolomeu Dias discovered the Cape Of Good Hope, and in 1498 Portuguese navigator Vasco da Gama sailed around the cape to discover a sea route to India.
It was during the late 13th and early 14th centuries that early faceted gemstones began to appear as the technology to work with such hard stones developed. The Renaissance gem-cutting trade developed in Belgium, but soon spread quickly around Europe.
The art of facetted gem cutting was perfected in Italy during the 16th century, followed by the ground-breaking ‘brilliant cut’ in the 17th century first created by Italian ambassador Jules Cardinal Mazarin.
After a run of 2000 years the Indian diamond mines were severely depleted, but in 1725 a spectacular new find in Brazil (in the mountainous regions of Bahia and along the Rio Jequitinhonha river near Tejuco) delivered the European market a new supply.
During the Renaissance period jewellery with gemstone setting began to dominate fashions.
Burgeoning trade routes around the globe meant they were more attainable, and they became increasingly popular with the wealthier noble classes (where previously in the Middle Ages the Royalty and the churches had been the only organisations with enough wealth to use gemstones in their richly-jewelled ceremonial objects).
The Industrial Revolution of the 18th and 19th centuries led to the growth of the middle classes, and suddenly another section of the populace could afford jewellery.
This demand in turn led to the creation of costume jewellery, which gave the appearance of precious materials and stones by using cheaper metals, glass and semi-precious stones.
As techniques and technology have progressed, the quality of diamond cuts has increased over the years and although styles of jewellery have developed and changed the use of gemstones, particularly diamonds, remains a constant to this day.
Types of gemstone
Main article: List of types of gemstone
There are a wide variety of gemstones, which are classified into different groups, species, and varieties.
Some are not minerals but naturally-occurring materials such as stones or organic material. Due to their appearance and use throughout history, however, they are still considered to be gemstones.
Main article: List of gemstone collecting terms
The world’s most expensive gemstone
The most expensive gemstone ever sold at auction is the 24.78 carat ‘fancy intense pink diamond’ sold in Geneva in November 2010.
The GIA (Gemological Institute of America) report stated that the diamond is Fancy Intense Pink, Natural Colour, VVS2 Clarity, and that it may be potentially flawless after surface polishing.
Featuring a classic emerald cut, the ring sold to a British dealer for a world record price of $45,442,500 (including buyer’s premium).
Other notable gemstones
Main article: List of notable gemstones
Notable gemstone collections and collectors
Main article: List of notable gemstone collections
Main article: List of notable gemstone collectors
Main article: List of gemstone dealers
Clubs and societies
Main article: List of gemstone collectors' clubs and societies
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