Skarn

A skarn is a rock made of calcium-rich silicate minerals, such as garnet, diopside, wollastonite and tremolite, that forms where hot fluids from an igneous intrusion react with limestone or dolomite. Skarns host many metal ores and industrial minerals, and some contain tremolite or other amphiboles in fibrous form.

Origin

Skarn is an old Swedish mining term for the hard silicate rock found around iron ore bodies. Geologists adopted it in the early twentieth century to describe the calc-silicate rocks formed by contact metamorphism and fluid alteration of carbonate rocks.

Significance in Asbestos Context

Skarns matter because they are one setting where amphiboles such as tremolite and actinolite grow, sometimes in asbestiform habit. Mines that worked skarn ores for metals, wollastonite or other minerals could expose workers to these fibers even though asbestos was never the product. Some talc deposits also formed where silica-rich fluids altered dolomite, and the related minerals can include tremolite. In litigation, the geology of a deposit can help experts explain why a product such as talc, wollastonite or crushed stone might contain amphibole fibers, and defendants may use the same geology to argue that the amphiboles there are non-asbestiform. For a worker in mining or quarrying, the type of rock mined may be an important part of the exposure history.

Example Sentence

The mine's geologic reports described a tremolite-rich skarn zone between the granite and the marble.

Related Terms

Contact Metamorphism, Wollastonite, Tremolite, Dolomitic Limestone, Carbonate Mineral, Metamorphism, Country Rock

Notes

• If you worked at a mine or quarry, note the rock types and products; geologists can check them for fibrous minerals.
• Company or government geology reports on a mine can be useful evidence; ask your lawyer about obtaining them.