Tigers Eye: Properties, Facts and Photos

What is Tigers Eye?

Tigers eye (or tiger eye) is a yellow and brown variety of quartz known for being chatoyant.

Chatoyancy, or chatoyance, is an optical phenomenon found in a few minerals but is relatively rare compared to other optical phenomena.

The extent to which this can be seen depends on the orientation of the fibres and the stone cutter's skill. Chatoyant gemstones tend to be cut as cabochons because the domed shape enhances the effect.  

When a chatoyant tigers eye stone is gently moved, the band of light also moves, creating an illusion of movement within the stone.

The word 'chatoyant' comes from French for 'cat's eye.'

Tigers eye is a relatively hard stone, which makes it easy to work with. On the Mohs scale of hardness, it grades 7.

Huge reserves of tigers eye can be found in Western Australia, an area rich in iron. South Africa also has vast reserves. The finest-grade tigers eye comes from Griqualand West in the Northern Cape.

It can also be found in southern Brazil, where iron-rich geological conditions are similar to those in South Africa and Australia. 

When tigers eye is heated, it changes colour. The brown variety, which is the most popular, is the stone people tend to be familiar with. Red tigers eye and black tigers eye are typically produced through heat-treatments.

Although tigers eye can have a natural red hue, most red tigers eye, also known as bulls eye, is heat-treated. During this process, the yellow limonite converts to red hematite, giving the stone a deep red colour.

Red tigers eye does not exhibit chatoyance because the natural fibrous structure of the quartz alters during the heat treatment, which affects the light-scattering properties responsible for this effect.

The Association of Tigers Eye with Asbestos

There is some concern regarding the presence of asbestos in tigers eye.

Until quite recently, it was widely believed that the crocidolite, a type of asbestos, had been replaced with silicon dioxide over millions of years.

In geology, when one mineral replaces another, the process is known as pseudomorphism. A pseudomorph looks like one mineral but is actually another. Although the shape or crystal structure of the original mineral remains the same, the mineral itself has changed. A new mineral replaces the original one.

Pseudomorph literally means 'false form'.
A scientific study conducted in 2003 found that no mineral replacement has occurred and that tigers eye is composed of crocidolite and quartz.

Many articles still claim that crocidolite has been replaced with quartz, but this detailed and respected study proves otherwise. 

The thought of asbestos being present often causes concern, but the danger comes from inhaling its dust or fibres. In tigers eye, the crocidolite is locked deep within the quartz, so presents no risk.

Asbestos was widely used on an industrial scale until the year 2000. It only becomes dangerous when microscopic fibres break away, become airborne and are inhaled. That's simply not possible when handling a solid piece of tigers eye stone because the asbestos fibres are encapsulated within the quartz.

It's worth noting that malachite is an ore of copper, so its dust is highly toxic. The microscopic crystalline silica particles in the mineral quartz are also dangerous if inhaled. Silicosis is a serious lung disease caused by inhaling these particles.

In fact, the dust or fibres from many minerals can be hazardous, but that doesn't mean they're dangerous to handle. They only become a health hazard when being cut, sanded or drilled.

Chatoyance in tigers eye is caused as light reflects off the crocidolite fibres. Please Note.

Blue Tigers Eye: Good to Know

Blue tigers eye is also known as Hawks Eye and Falcons Eye, although the latter is not used as often.

In brown tigers eye, iron associated with the crocidolite fibres becomes oxidised. These iron oxides (often grouped under the term ‘limonite’) give the stone its characteristic colour and chatoyant effect.

In blue tigers eye, the crocidolite fibres remain less oxidised, preserving their bluish-grey colour. The blue hue comes from iron in the crocidolite fibres that has undergone little or no oxidation.

'Oxidised' refers to a process where a substance reacts with oxygen, often leading to a change in its chemical composition or appearance. For example, when an apple is peeled and left to sit, it turns brown as it oxidises.

Article Photos

The photos of tigers eye in our article, including the red and black tigers eye in the pop-up photos, are from our collection.

The goethite pseudomorph after pyrite in our second photo is courtesy of Stan Celestian.