Fibrous Habit

A fibrous habit is a mineral's tendency to grow as fibers, crystals much longer than they are wide. All asbestos is fibrous, but not every fibrous mineral is asbestiform: asbestos fibers are also flexible, very strong, and made of bundles of even finer fibrils that can be pulled apart.

Origin

"Habit" is the mineralogist's word for the outward shape a mineral takes as it grows. Mineral descriptions have long used fibrous alongside terms such as acicular (needle-like), prismatic and bladed. The distinction between merely fibrous and asbestiform minerals became important as regulators and courts tried to define what counts as asbestos.

Significance in Asbestos Context

Experts on both sides of mineral cases use these words precisely, and the difference can decide a case. A fibrous mineral that is not asbestiform may be described as having brittle, rigid or non-separable fibers. Plaintiffs' experts often stress that fibrous non-asbestos minerals, such as erionite or the Libby amphiboles, cause the same diseases as asbestos, so the label matters less than the dimensions of the particles. When reading an expert report, it helps to note whether a particle is called fibrous, acicular or asbestiform, and on what evidence.

Example Sentence

The report described the anthophyllite as fibrous but not asbestiform because its fibers were rigid and did not split into fibrils.

Related Terms

Asbestiform, Habit, Acicular, Non-Asbestiform, Fibril, Erionite

Notes

• Ask your experts to explain in plain terms how they told fibrous from asbestiform particles.
• The same mineral can appear in more than one habit in a single deposit.