Peridotite

Peridotite is a dense, coarse-grained igneous rock formed deep within the Earth's upper mantle, composed mostly of the minerals olivine and pyroxene. When peridotite is altered by hot, water-rich fluids over geological time, a process called serpentinization, it can transform into serpentinite, which is the parent rock of chrysotile asbestos and is often associated with tremolite and other amphibole asbestos minerals.

Origin

The name was introduced in the 19th century, derived from "peridot," the gem-quality variety of olivine, which is the dominant mineral in the rock. French mineralogists popularized the term as the study of ultramafic rocks expanded in the 1800s.

Significance in Asbestos Context

Peridotite is essentially the geological starting point for most of the world's asbestos. When patients or their experts trace asbestos exposure back to a specific mine or product, the geologic story almost always begins with peridotite bodies that were uplifted to the surface and altered into serpentinite. Knowing whether a product's asbestos came from a peridotite-derived source helps experts identify which fiber types (chrysotile, tremolite, anthophyllite) are likely present and which mines or deposits the material came from, important for provenance analysis and for tying a defendant's product to a particular exposure.

Example Sentence

The geologist testifying in the case explained that the talc in the contested product was mined from a deposit formed in altered peridotite, which is why tremolite and anthophyllite fibers were found in the samples.

Related Terms

Serpentinite, Chrysotile, Tremolite, Ophiolite, Ultramafic Rock, Provenance Analysis

Notes

• If your exposure history involves talc, vermiculite, or industrial minerals, ask whether the source deposit was located in or near peridotite or serpentinite bodies. This affects which asbestos fibers may have contaminated the product.
• Preserve product packaging, brand names, and any documentation showing where a mineral product was mined; geologists can use mine location to determine if peridotite-derived asbestos contamination is plausible.
• In litigation, expect defense experts to dispute whether a specific deposit contained asbestiform minerals; a geologic provenance analysis tied to peridotite/serpentinite origin is often central to that debate.