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ASBESTOS (bulk): METHOD 9002, Issue 2, dated 15 August 1994 - Page 8 of 9

Table 1. Optical Properties of Asbestos Fibers Refractive Index (Approximate Values)

  • to

Elongation

5 to Elongation

Mineral

Morphology and Color

Chrysotile

Wavy fibers with kinks. Splayed ends on larger bundles. Colorless to light brown upon being heated. Nonpleochroic. Aspect ratio typically >10:1.

1.54

1.55

0.002 - 0.014

CummingtoniteGrunerite (Amosite)

Straight fibers and fiber bundles. Bundle ends appear broom-like or splayed. Colorless to brown upon heating. May be weakly pleochroic. Aspect ratio typically >10:1.

1.67

1.70

0.02 - 0.03

Crocidolite (Riebeckite)

Straight fibers and fiber bundles. Longer fibers show curvature. Splayed ends on bundles. Characteristic blue color. Pleochroic. Aspect ratio typically >10:1.

1.71

1.70

0.014 - 0.016 Interference colors may be masked by blue color.

Anthophyllite

Straight fibers and fiber bundles. Cleavage fragments may be present. Colorless to light brown. Nonpleochroic to weakly pleochroic. Aspect ratio generally <10:1.

1.61

1.63

0.019 - 0.024

TremoliteActinolite

Straight and curved fibers. Cleavage fragments common. Large fiber bundles show splayed ends. Tremolite is colorless. Actinolite is green and weakly to moderately pleochroic. Aspect ratio generally <10:1.

1.60 - 1.62 (tremolite)

1.62 - 1.64 (tremolite)

0.02 - 0.03

1.62 - 1.67 (actinolite)

1.64 - 1.68 (actinolite)

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94

Birefringence

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