Hole in Gravelroad caused by pipe-damage

[toonfandangl]

Interesting topic George especial the mention of asbestos.


I was under the impression that Tigers Eye (Mike mentioned this in a recent post)  was fossilised asbestos!! apparently not according to this report.

There has been a lot of trouble here in Australia with a company JAMES HARDIE and asbestos related diseases
there is a link below if anyone is interested.

www.abc.net.au/news/stories/2009/05/20/2575920.htm



The report below is boring so have highlighted the Tiger Eye..... Asbestos bit


New interpretation of the origin of tiger's-eye
Peter J. Heaney and Donald M. Fisher, Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA. Pages 323-326.
    The rich brown shimmer of tiger's-eye combines with a durable polish to make this lively gemstone a perennial favorite among jewelers and mineral collectors. Though tiger's-eye once was a highly valued rarity in western Europe, the discovery of abundant sources in South Africa in the 1870s sent its value careening downward; it now is one of the most affordable gems. For over a century, mineralogists believed that tiger's-eye was a kind of fossilized asbestos. Specifically, they assumed that tiger's-eye forms when a fibrous mineral called crocidolite is infiltrated with hot solutions rich in dissolved silica. Somewhat similar to the way petrified wood is formed, the solutions were presumed to dissolve the asbestos and replace it with quartz. Mineralogists call this process pseudomorphism-the exchange of one mineral with another while the shape of the first mineral is retained. Pseudomorphism serves as a record of a rock's "previous lives," and it is frequently exploited by geologists who are trying to unravel changes in Earth's ancient environment. Tiger's-eye has long been acclaimed in textbooks and museum displays as the archetype of pseudomorphic mineral replacement.
    Now those textbooks will have to be revised. Professors Peter Heaney and Donald Fisher at the Pennsylvania State University have examined tiger's-eye using a number of sophisticated techniques. Their analysis has revealed that pseudomorphism is not what underlies its elegant shimmer. Instead, they found that the chatoyancy, or cat's-eye reflection, seen in the gem is the result of tiny fibers of crocidolite asbestos that are completely encapsulated in quartz. The crocidolite and the quartz grew simultaneously inside microscopic cracks that opened as rocks experienced tectonic stresses during mountain-building events. The minerals were deposited in the cracks by solutions percolating through the fractured rocks.
    Interestingly, the quartz and the asbestos crystals nucleated on opposite sides of a single fissure and grew into each other as the cracks were sealed to make a quartz-crocidolite vein. Crocidolite is blue in color, and Heaney and Fisher found that the brown color of tiger's-eye is the result of tiny crystallites of iron oxide that formed more recently and decorate the surfaces of the crocidolite fibers. As the rocks were slowly rotated during repeated tectonic episodes, cracks were reopened but the direction of the asbestos growth changed. Since reflection of light from the crocidolite fibers is the cause of the cat's-eye effect, the zigzag chatoyancy that is a hallmark of tiger's-eye actually provides a history of the rock's displacement path during the collision of tectonic plates.

[Michael Alexander]

Thanks Frank, sitting here reading that piece, looking at my Tigers eye...... must get down to the beach sometime and find some more...

[toonfandangl]

Mike.  I still have some Tigers Eye that was made into jewelry by the Ovombo administrator a guy named "Steve Ettwin" I think that's the way his name is spelt.

Have mentioned his name in a few posts no response, maybe no Oldies still around that can remember that far back 1968---71.

He got his goldsmiths licence around that time and I think his gold mark was S. ETT. does it ring a bell with anyone.