Sapphire blue gemstone

Blue sapphire, a variety of corundum, is one of the most valuable gemstones, known for its hardness and intense color.

About this subject

Blue sapphire, a variety of the mineral corundum (crystallized aluminum oxide), gets its characteristic blue color from trace elements of iron and titanium in its crystal structure. With a hardness of 9 on the Mohs scale, it is second only to diamond, making it extremely scratch-resistant and suitable for everyday wear in jewelry. Major historical sources include Kashmir (India), Myanmar (formerly Burma), and Sri Lanka (formerly Ceylon), each producing specific blue hues: velvety blues from Kashmir, intense blues from Myanmar, and lighter blues from Sri Lanka. Today, gem-quality sapphires are also mined in Madagascar, Australia, and Thailand.

Sapphire has long been associated with royalty and the clergy, symbolizing wisdom, virtue, and fidelity. The engagement ring of Princess Diana, now worn by Catherine, Duchess of Cambridge, is a 12-carat blue sapphire surrounded by diamonds, further popularizing the gem. Famous sapphires include the Star of India (563 carats, from Sri Lanka, displayed at the American Museum of Natural History) and the Logan Sapphire (423 carats, also from Sri Lanka, at the Smithsonian Institution).

Gemologically, sapphire may contain rutile inclusions that cause asterism (a six-rayed star), common in star sapphires. Heat treatment is widely accepted to improve color and clarity, but untreated sapphires are rarer and more valuable. The largest consumer market for blue sapphires is Asia, particularly China and Southeast Asia, where they are used in both traditional and modern jewelry.

Frequently Asked Questions

What causes the blue color in sapphire?

The blue color in sapphire is caused by the presence of iron and titanium ions in the corundum crystal structure, through a charge transfer process between these elements.

Where are the finest blue sapphires found?

Historically, the best sapphires come from Kashmir, Myanmar, and Sri Lanka. Today, Madagascar also produces exceptionally high-quality gems.

Are all blue sapphires heat treated?

Many sapphires undergo heat treatment to improve color and clarity, but untreated sapphires are rarer and more valuable. The practice is common and accepted in the trade when disclosed.