Tiger Eye - (Tiger-Eye, Tigers Eye, Tigereye, Tiger’s Eye) - Mohs 6.5-7

Additional varieties: Hawks Eye, Tiger Iron, Marra Mamba, Pietersite

What all of these have in common is that light glides across the surface as the stone is moved, lighting up sections of the stone. This effect is called chatoyancy and is caused by the asbestos in these stones.

Where these stones differ is the colors and patterns.

The Progression:
These rocks start with hawk’s eye. The chatoyancy is created by microscopic fibers of crocidolite encapsulated within quartz.

Crocidolite (blue asbestos) is a gray-blue to green fibrous form of the amphibole mineral riebeckite. Blue (and the more rare green) tiger’s eye has preserved the original color of the riebeckite. As you move the stone, the crocidolite fibers come into a reflective orientation with your eye and bands of color illuminate. When you rotate the stone into a non reflective orientation, the bands become dark.

Crocidolite is an iron sodium silicate and as the iron oxidizes, it becomes golden brown, creating the golden brown tiger eye most people are familiar with.

Pietersite is then formed by a process known as brecciation. The fibrous structure of hawks eye and tiger eye are broken up via the earth’s geologic process. The tiny fragments are later cemented back together naturally by quartz, creating a stone with multiple hues and superb chatoyancy. The chatoyancy is no longer in bands, but occurs in swirls and patches.

Pietersite, first found in Africa, gets its chatoyancy from crocidolite. Pietersite later found in China is slightly different from the African variety, both in color and in the type of asbestos causing the chatoyancy. In additon to (or perhaps instead of) crocidolite, it has other asbestos fibers like chrysotile and torendrikite.

Chrysotile is a fibrous form of serpentine. Individual fibers are white and silky, but the aggregate in veins is usually green or yellowish. Torendrikite is an amphibole asbestos and is dark blue.

The Varieties:
Tiger Eye is fairly well known by many people. It is a gold and brown stone and is cut to emphasize the bands that light up across the stone. Where possible, it is cut to show off a "cat’s eye" - just a slit of golden color in the middle of an oval stone. However, multiple bands and wider bands create very pretty stones.



Hawks Eye is a blue variant of tiger eye. (Last image above.)

Green Tiger Eye is natural, but rare.

Red Tiger Eye - meaning a uniformly red stone with an appearance like the golden tiger eye or the blue hawks eye, is due to heat treatment, either by man or by nature, as in a hot brush fire.

Australian Tiger Iron -

In the Pilbara region of Western Australia. Tiger Eye is found intermixed with hematite and iron pyrite in a magnetitie rich, red/brown/black host rock called jaspillite. There are 2 commercially important Banded Iron Formations there, called the Brockman Iron Formation and the Marra Mamba Iron Formation.

The safest name for the material is Australian Tiger Eye, but it is quite distinctive looking and normally gets called Australian Tiger Iron. I’ve seen the highly striated material referred to as Tiger Iron Matrix.


Other names also get attached to Australian Tiger Eye, some based on where it came from and some based on coloration. The terms Brockman Tiger Iron and Marra Mamba Tiger Iron imply that the tiger iron is from those specific formations. The first 3 pictures of tiger iron are pieces from the Marra Mamba formation. However, many people argue that the term Marra Mamba should only be applied to tiger iron that meets a specific coloration.

The term Marra Mamba (often mispelled as mara mamba) is now pretty much reserved for the "non-golden" tiger iron from the marra mamba formation. It was mined from isolated pockets that have been mined out, although new deposits could be found. It is richly colored - browns, reds, blues, greens, mustards, silvers - and highly chatoyant.

Pietersite -

Pietersite is found in South Africa (Nambia) and China (Henan Province). It is brecciated, which means that somewhere along the line it got broken up, mixed up, and recemented by silica. The result is that the chatoyancy, instead of going in bands, goes in swirls and other patterns.

The colors range from midnight blues to browns, reds, yellows, and sometimes greens. The colors are often intermingled in swirled patterns. The Chinese variety has more red and golden/red combinations.