EDUCATION
RUBY FULL GUIDE
CHARACTERISTICS OF RUBY
Etymology: From the Latin rubeus, meaning red stone
Family: Corundum
Chemical composition: Aluminum Oxide/Chromium
Hardness: 9 on the Mohs scale
Density: 3.9 – 4.05
Optical properties: Negative uniaxial
Refractive index: 1.762 – 1.770
Birefringence: 0.008 – 0.01
Crystal system: Trigonal
THE ORIGIN OF RUBY
The famous Mogok valley in Myanmar (formerly Burma) has for several centuries been the home of the most beautiful rubies in the world, renowned for their unique red color. These mines have now almost run dry, which has increased the value of the Myanmar ruby considerably.
Alongside Myanmar, Mozambique is one of the top global producers of rubies. Although they were mined illegally by independent miners for years, production is currently overseen by a partnership between mining company Gemfields and the government.
Like most gemstones, the origin of a ruby has a huge effect on its value. As such, the most renowned and therefore most expensive rubies come from Myanmar, the Luc Yen region in northern Vietnam and the Himalayas. But this red corundum stone can also be found in other parts of the world, such as Mozambic, Sri Lanka, Madagascar, Malawi, Kenya, Tanzania, Thailand and even Greenland, where a new mine has been recently discovered.
Wherever they are sourced from, the large majority of rubies are cut and sold on the market in Thailand.
CARAT
The carat is used to assess the weight of precious stones. It is important to know that the more a stone weighs in carats, the more valuable it is. For example, a 1-carat ruby weighs 0.2 grams. It is very difficult to find natural good quality rubies weighing more than two carats.
But be careful not to confuse carats with karats, which is a unit used to determine the purity of precious metals.
THE COLOR OF RUBY
Ruby is a red gemstone and its color is prized above all else, including clarity and weight, when it comes to assessing its value. This corundum stone owes its red color to the fairly high concentration of chromium in its composition. It can also vary in color depending on its origin, ranging from orange-red all the way to a purplish blue or even brownish red.
Rubies sourced from Myanmar are the most renowned and are prized for their pure red color. In fact, certain Mogok valley rubies have been dubbed 'pigeon blood' rubies for their vivid and highly saturated color that has just the slightest touch of fuchsia. These rubies are extremely rare and very expensive. This name can only officially be used for rubies from Myanmar but is often used liberally. Technically it should only be used by recognized laboratories.
Rubies with a similar color and properties to the Myanmar stones can also be found in one particular mine in northern Vietnam, as well as in the Morogoro region of Tanzania.
However, rubies from Central and South-East Asia tend to contain a touch of pink. Rubies from East Africa often have a slight orange hue, such as rubies from Mozambique or the Winza region of Tanzania. And Madagascan rubies are known for their purplish hue.
HUE
The hue of a gemstone describes its shade. Rubies have many different hue combinations that make each stone completely unique.
SATURATION
Saturation refers to the degree of color intensity of a gemstone. This is an essential indicator in the valuation of ruby.
TONE
Tone refers to the brightness of a ruby, describing whether the color falls towards the light or dark end of the spectrum. The most sought-after rubies tend to have a medium to medium-dark tone.
THE CLARITY OF RUBY
When buying a ruby, clarity is a far less important factor than color as all natural rubies contain small impurities. These impurities, which are also known as inclusions, are more or less visible to the naked eye, but there is no such thing as a perfectly 'clean' ruby, i.e. without inclusions. However, as rubies with less visible inclusions are rarer, they are naturally more expensive.
CUTS & SHAPES
Ruby can be cut into a variety of different shapes, including oval, heart, pear, cushion and round. But the most common ruby cut is the oval cut, as it involves the least amount of loss of raw material during cutting.
Industry standards dictate that gemstones must be faceted in line with certain proportions (table plane perpendicular to the main C-axis) in order to bring out the best possible hue, but perfectly cut rubies are very rare.
The stone's culet is often slightly off-center or cut more deeply than is standard to bring out the best color possible.
OVAL RUBY
ROUND RUBY
PEAR RUBY
CUSHION RUBY
CALENDAR
The ruby is the birthstone of anyone born in the month of July. It is also used to celebrate 35 years of marriage in France and 40 years of marriage in the US (ruby wedding anniversary).
FAMOUS RUBIES
The Saint Wenceslas Ruby
The Saint Wenceslas Ruby was made for by Charles I of Luxembourg and is a truly exceptional precious stone the likes of which are rarely seen today. This uncut 250-carat ruby adorns a royal crown which is kept in the St Vitus Cathedral in Prague.
Sunrise Ruby
The Sunrise Ruby is a 25.59-carat 'pigeon blood' Myanmar ruby. It is set into a ring that was sold at Sotheby's in May 2015 for over $30 million, when it simultaneously broke the price-per-carat record for a ruby, which is over $1 million per carat.
Carmen Lucia Ruby
The Carmen Lucia Ruby was discovered in the 1930s and is a 23.1-carat stone boasting exceptional clarity. It was given to the Smithsonian Institution in Washington, DC by businessman Peter Buck in remembrance of his late wife Carmen Lucia. It is widely considered to be one of the most beautiful Myanmar rubies ever found.
Richard Burton Ruby
The Richard Burton ruby is an exceptional 8.24-carat Myanmar ruby set into a diamond ring given to Elizabeth Taylor by Richard Burton in 1968. It was sold for $4.2 million at Christie's in 2011, which adds up to over $500,000 per carat.
TREATMENT
Like sapphires, it is extremely rare to find high quality natural rubies that have not undergone heat treatment. The most common method for enhancing ruby consists of heating the stone at a temperature of 1300°C so that its color intensifies and its inclusions crystallize and become less visible. This type of heat treatment, known as embellishment, is used on the majority of rubies on the market, which is why purchasing a non-heat treated ruby is an excellent investment. However, it must have a certificate from a recognized laboratory (e.g. GIA, Gubelin, GRS, IGI, AIGS, etc.).
There are other types of changes that can be made to a stone, including lead-based treatments, but these are not officially recognized by industry standards.