Information on tiger eye, pietersite, marra mamba, Arizona tiger eye,
and hawks eye.
HISTORY & FACTS:
First of all, tiger's eye, tigereye, tiger eye and tiger-eye are all accepted ways to write this name.
Up until recently tiger eye has been considered to be pseudomorph but new evidence proves otherwise. It has long been thought that the crocidolite fibers were replaced with quartz much like the replacement that happens in petrified wood. This new evidence proves this may not be the case and that quartz and the crocidolite co-exist. To read more Click Here
Tiger eye has a fibrous structure and in the lapidary shop must be oriented properly to get the chatoyance and/or the "cats eye" effect. Cuts must be exactly parallel to the length of the fibers to get full chatoyance. If the saw cut is perpendicular, or 90% to the fibers, you end up with a lifeless, dark brown to black stone with no chatoyance or light play at all. Orientation of cutting is critical to getting good chatoyance and color out of tiger eye.
These fibers in Tiger Eye may be up to about two inches long and very thin. Most are only 0.001 millimeters, or 0.000039 inches in diameter and are not always straight making it even harder at times to cut good chatoyant stones.
In most cases but not always, red tiger eye is not a natural occurrence. It is usually a result of heating and can be done using the kitchen oven. Here's a basic recipe for heat treating tiger eye.
To protect the tiger-eye from thermal shock during heating cover slabs of ordinary, gold tiger eye in fine clean silica sand, at least 3" all around the slab.
Place the metal container in a cold oven and increase the temperature 50°F every hour until it reaches 400°F. Then turn the oven off AND DO NOT open the door. Allow plenty of time for the container to cool all the way through. (If you heat treat tiger eye to sell BE SURE you let it be known it has been treated, it's only right and it's the law.)
There are natural occurrences that tiger eye can be found with red color. And other known ways have been from brush fires where the deposits are found and also when miners would build fires next to the seams to help crack it up into smaller pieces, remember most of these miners had nothing but hand tools to work with.
Not long after tiger eye was first discovered for lapidary the world famous Idar-Oberstein lapidaries discovered by using hydrochloric or oxalic acid they could bleach tiger eye to an evenly colored light, translucent yellow. When cut properly they produced "cats eye" stones that look much like the rare variety of chrysoberyl but can be distinguished very easily between the two by gemologists.
Other treatments but not usually done, never by me, but some do do it. In pietersite and bighamite stones especially, it is very common to run into pits, cracks or voids called vugs. These are sometimes filled with wax, super glue or opticon in the last steps of sanding and polishing the stone. I never do any of these treatments but as I said it is and has been done by others.
There are many other types of stones that display a "cats eye" or shimmering chatoyance but we'll get into them later. The word "Chatoyant" comes from the French word for "cat" or to glow like a cat's eye.
Tiger eye is the anniversary gemstone for the 9th year of marriage
PIETERSITE is a chatoyant, quartz and crocidolite asbestos. Its appearance is quite different because it's been broken into fragments (brecciated), stirred around if you will, and recemented by silica. The fibers are wavy unlike the gold tiger eye that normally has straight fibers. The resulting patchwork is in shades of blues, yellows, greens, brown, and reds Sometimes areas with clear quartz is also found and I like to cut stones leaving some of the water clear quartz areas when I find them..
Pietersite is named for Sid Pieters, a well-known gem and mineral dealer is from Windhoek, Namibia who imported it to Idar in the 1970s.
One of the major sources of Pietersite is Namibia, an area about 2,000 miles from the tigereye locality in South Africa. It was found as rounded cobbles in the soil on a farm in the neighborhood of Outjo, in the Kuraman district, but its actual source has never been located. It is also reported that it has become vary scarce in Africa and South African authority Windisch says it is all mined out and rarely avalible from "old" stock.
The other major source of Pietersite is from the Henan Province of China. It made its apperance on the open market in the late 1990's. It was originally found in the 1950's but no one considered using it for jewelry-making. The Chinese had no idea how popular it would become in the rest of the world. This pietersite is very similar to that found in Nambia except that it has more red and golden-red combinations and is narmally more fractured from my experiance with the rough.
The Chinese material contains both chrysotile and crocidolite fibers and petrification is very strong. Unfortunately, as the material gets popular, the source is being exhausted and one mine has been reported to have had to close due to ground water flooding it.
Marra Mamba is considered the Rolls Royce of all tiger eye by many collectors and lapidarists.
In the Hamersley Ranges of the Pilbara region in Australia there are a few small areas where Australian tiger-eye has been found. The best known area is near Mount Brockman. A ridge of hills a few miles long, has produced good quality golden colored material from a number of small deposits. ONLY TWO of these deposits have ever produced the "true" marra mamba a very rare type with reds, blues, yellow gold and greens! This has been mined out for nearly twenty years now.
This material is actually a serpentine and is produced when water from magmas changed igneous rocks. The fibrous veins are Crysotile, a generic term for undifferentiatied asbestiform Serpentine Group species. The species are clinochrysotile, orthochrysotile, and parachrysotile. Lizardite and antigorite are closely related Serpentine Group species.
The cabochons cut from this material are fantastic for chatoyance, better than all others IMO and has a translucent amber color. The chatoyance is so bright in the best examples it makes it very difficult to get good pictures. This is one stone you seldom see and when you do see it in life you will want all you can get.
It is soft, so pieces of jewelry like pendants are recommended.
Many years ago some of this material was collected from the asbestos mines near Globe Arizona that was opalized.
Very little was cutable and very little had wide enough veins to cut stones but what was found that would qualify was cut into cabochons that had a very nice fine line cats eye effect! The late Martin Koning had several of these 'cats-eye' stones in his collection.
Natural gold, blue and red tiger-eye slab. US dime for size.
Rare natural green tiger-eye
Binghamite is known as the U.S. version of tiger eye and is found in the Cayuna iron range of northern Minnesota. Basically it is fibrous quartz in which the replaced fibers are a red hematite and yellow goethite iron rather than crocidolite. It is also called Cyunite by a few people.
Bill Bingham, a lapidarist from St. Paul discovered this material on the mine dumps in 1936. He found it to be an excellent lapidary material with chatoyant reds, browns, golds and blues. Much of it contains metallic hematite which adds interest to the stones. Sometimes it is also found brecciated.
Silkstone is basically the same material but sometimes has fibers that are shorter, twisted and with greater color variations. It is also less likely to have white quartz inclusions. If the Goethite inclusions are not parallel, but disordered, the stone is known as Silkstone.
This material is getting harder and harder to find and good specimens are very expensive if you can find them.
Tigereye is still being mined and sold today as Marra Mamba. Some of the new material is nice but not near as colorful or chatoyant as the original deposits.
Tiger-eye, pietersite, binghamite and silkstone Information
There is another tiger-eye found in Arizona that is more like the quartz-crocidolite variety. The AZ tigereye material begins with a quartz matrix and golden crocidolite stringers, and proceeds all the way to common opal with no distinguishable fibers remaining - only patches of color.
This picture, courtesy of Jim Small of Small Wonders Lapidary.
California Tiger's Eye
The California type is a silica-impregnated, white-to buff-colored, massive, fibrous tremolite (another asbestos mineral) that was collected for many years at Iowa Hill in Placer County. It is sometimes called Placer County tigereye.
Colors can vary due to the iron and/or magnesium content. However, true tremolite is predominantly magnesium rich and the more iron the stone has the more green it becomes.
Information on Marra Mamba tigers eye, hawks eye, Pietersite, Binghamite, Arizona tiger eye, Silkstone, African Tiger-eye. Treatments, origins and more.
Tiger iron comes from the Ord Ranges near Port Hedland in Western Australia's Pilbara region and is a banded iron formation or jaspilite that has alternating layers of black & brown hematite/magnetite, red jasper & chatoyant golden tiger eye..
Some has visible streaks of red jasper with the tiger's eye. If it's mostly jasper, it is usually called Tiger's Eye Jaspilite.