A Survey of Fibrosity of Fibrous Amphiboles Larry S. Pierce Fiberquant Analytical Services Phoenix, AZ

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

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

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

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 plot aspect ratio vs fiber width using log/log axes

Fibrosity Chart – very fibrous

Fibrosity Chart – not so fibrous

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

Cast of Characters

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

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) (photos/data)