Introduction to Rubies: Origin, Properties and Formation

Rubies, the red variety of corundum, have fascinated mankind for centuries with their intense colour. These precious gemstones, often referred to as the ‘king of gemstones’, are characterised by their exceptional beauty and rarity.

History and culture
The exact origins and first use of rubies are unknown, but historical records and ancient texts point to their origin in Sri Lanka. In the Bible, the red gemstone is mentioned four times and in ancient Indian legend, the ruby is considered the first gemstone created by God.

During the Middle Ages, coloured stones such as sapphires were popular with kings, but after the Renaissance, rubies and emeralds rose to become the most sought-after stones. There were no ruby mines in Europe, so rulers had to rely on traders from the East who brought rubies from Sri Lanka and Burma.

In the 20th century, rubies, once reserved for the nobility, were increasingly used in jewellery. The discovery of new mines led to the growing popularity and visibility of rubies, worn by maharajas and actresses. The demand for rubies is particularly strong in Asia and the discovery of large deposits in Mozambique in 2009 ensures a promising future for the ‘king of gemstones’.

Physical and chemical properties
Rubies consist of aluminium oxide (Al2O3) and get their red colour from the trace element chromium (Cr). These elements are crucial for the formation of rubies. Aluminium-rich rocks such as mica schist must interact with chromium-rich rocks such as ultramafic greenstones to form rubies. Without chromium, there would be no rubies.

Rubies are the hardest mineral after diamonds and have a Mohs hardness of 9. They are characterised by high light refraction and transparency, which leads to their brilliant shine.

Variety of colours
Rubies are available in various shades of red, from pale pink to deep blood red. The most sought-after colour is the so-called ‘pigeon's blood red’, which is most frequently found in rubies from Myanmar (Burma). The intensity of the colour is influenced by the content of chromium and other trace elements.

Formation and occurrence
Rubies are formed under exceptional geological conditions. There are three main types of geological environments in which rubies are found:

Marble deposits: These are the best known worldwide. Famous examples are Mogok in Myanmar, the Hunza Valley in Pakistan and Jegdalek in Afghanistan. These rubies often contain little iron, which leads to a strong red fluorescence that gives the rubies their coveted ‘inner glow’.

Metamorphic rocks with amphibolite: Examples include deposits in Mozambique, Tanzania and Greenland. Rubies from Greenland are around three billion years old.

Volcanic rocks (basalt): These deposits are found in Thailand and Cambodia.

Today's ruby mining
The early ruby deposits were discovered in Sri Lanka (Ceylon), later in Afghanistan, Myanmar (Burma) and Thailand (Siam). In the 20th century, new ruby-producing countries such as Kenya, Tanzania, Mozambique, Madagascar, Vietnam, Tajikistan and Greenland came to the fore.

The treatment of rubies became more important in the 20th century. Low-grade rough stones can be enhanced by traditional heat treatment or other methods. Most rubies on the market are treated to improve their appearance. High quality, untreated rubies are extremely rare and are highly prized at auction and by leading jewellers.

Rubies as an investment
Rubies are a prime choice for investment, especially in times of economic uncertainty. Their rarity and beauty make them a stable investment that is ideal for diversifying an investment portfolio. Investing in rubies can offer protection against inflation while providing attractive capital appreciation.