Sapphire

Sapphire is a precious gemstone, a type of the mineral corundum. It is made mostly of aluminium oxide with tiny amounts of other elements like iron, titanium, and chromium. Sapphires are most well-known for their bright blue color, but they can also be yellow, purple, orange, or green. When red, corundum is called a ruby instead of a sapphire.

Sapphires are very hard, ranking 9 on the Mohs scale, which measures how hard a mineral is. This makes them very durable and useful beyond just jewelry. They are used in things like watch crystals, special electronic parts, and strong windows for devices that need to see infrared light.

People have used sapphires for thousands of years in jewelry because of their beautiful sparkle and lasting quality. Today, sapphires can also be made in labs for industrial uses, where they help make strong and clear materials for technology.

Natural sapphires

Sapphire is one of the two gem-varieties of corundum, the other being ruby (defined as corundum in a shade of red). Although blue is the best-known sapphire color, it occurs in other colors, including gray and black, and can also be colorless. A pinkish orange variety of sapphire is called padparadscha.

Significant sapphire deposits are found in Australia, Afghanistan, Cambodia, Cameroon, China (Shandong), Colombia, Ethiopia, India (Jammu and Kashmir), Kenya, Laos, Madagascar, Malawi, Mozambique, Myanmar (Burma), Nigeria, Rwanda, Sri Lanka, Tanzania, Thailand, United States (Montana) and Vietnam.^{: 431–707}  Sapphire and rubies are often found in the same geographical settings, but they generally have different geological formations.

Every sapphire mine produces a wide range of quality, and origin is not a guarantee of quality. The cost of natural sapphires varies depending on their color, clarity, size, cut, and overall quality. Sapphires that are completely untreated are worth far more than those that have been treated. Geographical origin also has a major impact on price. For most gems of one carat or more, an independent report from a respected laboratory such as GIA, Lotus Gemology, or SSEF, is often required by buyers before they will make a purchase.

Colors

Sapphires that are not blue are called "fancy" sapphires. These can be yellow, orange, green, brown, purple, violet, or nearly any color. "Parti sapphires" have two or more colors in one stone.

Blue sapphires can have mixes of blue with violet or green. The purest blue sapphires are the most valuable, but personal taste affects what people like best. One very large blue sapphire is the 423-carat Logan sapphire, kept in the National Museum of Natural History in Washington, D.C.

Pink sapphires range from light to dark pink, with deeper pink meaning higher value. In the United States, a stone must be a certain pinkness to be called a ruby; otherwise, it is a pink sapphire.

Padparadscha sapphires are a rare light pink-orange color, originally from Sri Lanka but also found in Vietnam and East Africa. They are among the most valuable fancy sapphires.

Star sapphires show a star pattern when lit from above. This happens because of tiny lines inside the stone. The largest known star sapphire is the Star of Pure Land, found in Sri Lanka in 2025, weighing 3536 carats.

Color-change sapphires look different in different lights—they can be blue in daylight but purple indoors. These come from places like Madagascar, Myanmar, Sri Lanka, and Tanzania.

Cause of color

Rubies are a type of corundum that appear red because of tiny amounts of chromium. This chromium changes the way the stone absorbs light.

Blue sapphires get their color from a process where electrons move between different minerals. This movement absorbs yellow light, making the stone look blue. This can happen when tiny amounts of iron and titanium are present.

Purple sapphires contain small amounts of chromium, iron, and titanium, which mix to create different shades. Very clear sapphires, with almost no impurities, are rare and were once used like diamonds in jewelry. They are now often used as smaller decorative stones.

Mining

Sapphires are found in places called alluvial deposits or underground mines. Some places where people find sapphires include Afghanistan, Australia, Myanmar/Burma, Cambodia, China, Colombia, India, Kenya, Laos, Madagascar, Malawi, Nepal, Nigeria, Pakistan, Sri Lanka, Tajikistan, Tanzania, Thailand, the United States, and Vietnam. Sapphires from different places can look different and have unique features.

Some famous sapphires, like the Logan sapphire, the Star of India, the Star of Adam, and the Star of Bombay, come from mines in Sri Lanka. Madagascar is a big producer of sapphires, especially around the town of Ilakaka. In North America, sapphires are mainly found in Montana, especially near places like Helena, Montana, Deer Lodge, Montana, and Philipsburg, Montana. Kashmir, in India, is also known for its special blue sapphires.

Treatments

Sapphires can be treated in different ways to make them look clearer and more colorful. One common way is to heat the sapphires in special furnaces. This heating can change the color of the sapphire to a deeper blue and can also make some tiny lines inside the stone less noticeable.

There are also other treatments, like adding tiny amounts of different materials to change the sapphire's color. These treatments can create many different colors, but they need to be clearly told about when selling the sapphire, so people know what they are buying.

Synthetic sapphire

In 1902, a French chemist announced a way to make synthetic ruby crystals. This method, called the flame-fusion process, involves adding fine powder to a special flame and letting it form a crystal on a pedestal. Later, this same method was used to create blue sapphire by adding certain elements that give sapphire its blue color. The process creates crystals without many natural flaws.

Chemical additives can be used to make sapphires in many colors, not just the natural ones. Modern methods improve on the original technique to grow larger, clearer crystals. Synthetic sapphire is used in many products because it is very strong, very clear, and can handle high temperatures. It is used in watch crystals, phone screens, and special windows for machines and military equipment. It is also used in tiny parts for computers and lights, helping them work better and last longer.

Historical and cultural references

The word "sapphire" comes from many languages, starting from Hebrew and moving through Greek, Latin, French, and finally to English. Long ago, people thought sapphires could make the planet Saturn kind to the person wearing them.

In the Middle Ages, people in Europe used the word "sapphire" for blue crystals of a mineral called corundum. Sapphires are special gifts for a 45th wedding anniversary, and a "sapphire jubilee" happens after 65 years. For example, in 2017, it was the sapphire jubilee of Queen Elizabeth II’s time on the throne.

Sapphires are also the birthstone for September. Some Italian traditions say sapphires can help with eye problems and sadness. Even Mary, Queen of Scots had a sapphire she used for this purpose. The sapphire is also the official state gem of Queensland, a state in Australia, since August 1985.

Notable sapphires

There are many famous sapphires and rubies listed in a book called Ruby & Sapphire: A Gemologist's Guide.