Zircon occurs naturally in a large range of colours including: yellow, red, orange, brown, green, and blue. Heat treatment is often used to produce stones which are colourless, golden brown, or sky blue. Many of the available colours are very attractive, and zircons also have a high dispersion, and therefore show good "fire". Probably the best known colour is the very startling blue. Zircon is slightly brittle, and therefore should not be ill-treated, but otherwise it is quite durable and suitable for use in jewellery. Sadly it is not currently very popular, and this may be because its name is easily confused with the inexpensive synthetic cubic zirconia. (Cubic zirconia does not occur naturally).

Its great variability is caused by the natural radioactive decay of small amounts of uranium or thorium causing the crystal structure to break down into amorphous silica and zirconia. Heat treatment appears to reverse much of the deterioration in the crystal structure, so that "low" types can be converted successfully to "high" types. There are also intermediate types.

Zircon occurs in a wide range of colors but for many years, the most popular was the colorless variety which looks more like diamond than any other natural stone due to its brilliance and dispersion.

Today the most popular color is blue zircon. Most blue zircon, which is considered an alternate birthstone for December, is a pastel blue, but some exceptional gems have a bright blue color. Zircon is also available in green, dark red, yellow, brown, and orange.

Zircon occurs in a wide range of colors but for many years, the most popular was the colorless variety which looks more like a diamond than any other natural stone due to its brilliance and dispersion.

ZIrcon Today the most popular color is blue zircon. Most blue zircon, which is considered an alternate birthstone for December, is a pastel blue, but some exceptional gems have a bright blue color. Zircon is also available in green, dark red, yellow, brown, and orange.