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A Survey of Fibrosity of Fibrous Amphiboles

A Survey of Fibrosity of Fibrous Amphiboles. Larry S. Pierce Fiberquant Analytical Services Phoenix, AZ lspierce@fiberquant.com. Asbestiform vs. Non-asbestiform. mineral habit is a macroscopic property (naked eye, hand loupe or stereoscope)

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A Survey of Fibrosity of Fibrous Amphiboles

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  1. A Survey of Fibrosity of Fibrous Amphiboles Larry S. Pierce Fiberquant Analytical Services Phoenix, AZ lspierce@fiberquant.com

  2. Asbestiform vs. Non-asbestiform • mineral habit is a macroscopic property (naked eye, hand loupe or stereoscope) • microscopic properties (PLM, SEM, TEM) of asbestiform minerals vary • old timer’s “tremolite asbestos, but brittle” indicates that >100 years ago, it was recognized that all that is asbestiform is not the same

  3. Both are asbestiform actinolite • 1st is straight at any magnification; shiny clear-white under stereoscope; kind of chunky @100x though fibrous; not much brooming • 2nd is flexible; dead-white under stereoscope; can hardly be seen @100x; lots of brooming

  4. How to Quantify the Differences • Average Aspect Ratio • Graph of Aspect Ratio Frequency • Quantitative Fibrosity Measurement (Chatfield 2010, 2011)

  5. Fibrosity procedure Chatfield (Beard Conference, 2010): • grind sample in mortar & pestle • (fractional extraction) • Suspend & prepare TEM drop mounts • measure L & W ~200 fibers >5 um long @10,000x • plot aspect ratio vs fiber width using log/log axes

  6. Fibrosity Chart – very fibrous

  7. Fibrosity Chart – not so fibrous

  8. Index of mineral properties • Fibrosity chart procedure is intuitively satisfying – each fiber is plotted • No matter how asbestiform/non-asbestiform, there tend to be at least a few data points outside/inside the 20:1 box • Good mineral property index – every example seems to be on scale • Let’s define F.I. = % fibers inside the box • What variation in F.I. is normal? examples of actinolite, tremolite and anthophyllite

  9. Cast of Characters

  10. Conclusions • Asbestiform tremolite, actinolite and anthophyllite present a broad and continuous range of fibrosity index • Little or no correlation of fibrosity index to chemistry • Little or no correlation to mean fiber length • Correlation to mean width • Correlation to mean aspect ratio

  11. Moral of the Story • Instead of referring to an amphibole sample or deposit as merely asbestiform or non-asbestiform, we should rather specify how asbestiform (Fibrosity Index or Confirmed Asbestos or something similar) • http://www.fiberquant.com/johnson2011.htm (photos/data)

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