Topaz: Properties, Facts and Photos

Topaz is known for its hardness, clarity, and wide range of colours, although most topaz is colourless. Despite being widely used in jewellery, it can be difficult to cut because it breaks and chips easily.

Contents 1. What Colour is Topaz 2. Topaz Properties (geology) 3. Article Pictures 4. Shop Topaz

What Colour is Topaz?

Although known for its wide range of colours, most topaz is colourless. This material is sometimes called white topaz.

Impurities of titanium, iron (often hematite) or chromium produce shades including red, pink, violet, purple, blue, orange, brown, and green.

Imperial Topaz, one of the most sought-after varieties, can exhibit hues of orange, pink, or red, often within the same crystal.

Although blue occurs naturally, it's very rare, so most blue topaz gemstones are produced by irradiating colourless topaz, followed by heating to stabilise or adjust the colour.

Depending on the treatment, three shades of blue can be produced. Although many gemstones are irradiated, the practice is mostly associated with topaz.

Sky Blue is the most popular variety of blue topaz. London Blue is more intense, with a darker tone and deep saturation. The colour of Swiss Blue is sometimes described as 'electric blue'.
Colourless topaz was first irradiated to produce a blue stone in 1947.

Scientists believe gemstones exposed to radiation pose no risk to human health. Before being handled, they must be securely locked away to allow any measurable level of radiation to decay.

Sky Blue Topaz is usually stored for a couple of months. London and Swiss Blue are left for considerably longer, so are more expensive.

Blue topaz that's been irradiated should be protected from intense heat and sudden temperature changes. At 500 degrees Celsius (932°F), the stone's colour begins to fade.

When yellow to reddish-brown topaz is heated at a relatively low temperature, if impurities of chromium are present, the stone turns a rich shade of pink or purplish-red. 

Green and orange topaz turn blue after being heated at various temperatures. Orange topaz turns a very dark or rich shade of blue.

Another reason topaz is heated is to modify or stabilise colour, as some natural colours can fade with prolonged exposure to sunlight. This is particularly prevalent with brown topaz from Siberia and Utah.

Historically, all yellow-coloured gemstones were believed to be topaz. Only in the last two hundred years was it discovered that other minerals could also be yellow.

For many years, yellow sapphire was called Oriental Topaz. Even today, some varieties of quartz, particularly citrine and smoky quartz, are incorrectly labelled as topaz. 

Topaz and quartz are two different minerals.

The Ostro Stone is the largest cut blue topaz gemstone in the world. This flawless gem weighs approximately two kilogrammes. It was cut from material mined in Minas Gerais, Brazil, and was heat-treated prior to cutting.

On the Modern, Traditional, and Ayurvedic Birthstone Charts, topaz is the birthstone for November. Pearl is November's birthstone on the Mystical Birthstone Chart.

On the Modern chart, blue topaz is the birthstone for December

Properties of Topaz (geology)

Topaz is a silicate mineral composed of aluminium, silicon, oxygen, and fluorine. It grades 8 on the Mohs scale of hardness.

Topaz breaks easily along specific planes of weakness in its crystal structure. In geology, this is known as cleavage. This characteristic, along with the fact that topaz chips easily, makes cutting and polishing more difficult.

Flaws or inclusions can increase the chance of a stone cleaving. Topaz is also sensitive to heat and can break or shatter even when heated gently at a relatively low temperature.

Repairing topaz in jewellery is difficult and risky because pressure or a sudden change in temperature can damage the stone.

Topaz can be found in several countries around the world. The state of Minas Gerais in Brazil has long been the world's largest supplier.

Article Pictures

The topaz at the top of our article is a museum piece from Pakistan. The colourless topaz in the second picture is on display in the Natural History Museum of Los Angeles.

The topaz in the third picture is from Utah, USA. The second and third photos are courtesy of Stan Celestian.

The Sky Blue Topaz gemstones are from our collection.

Pop-up photos
Brown topaz: Courtesy of Géry Parent. Red Topaz, imperial topaz, smoky topaz, peridot: Courtesy of Stan Celestian.

Blue topaz: Courtesy of Alan English.