When was Chrysotile NOT Asbestos? 1891

I was reading Facebook the other day and saw a question on whether the the types of fibers which are considered to be “asbestos” have changed through the years. I decided to blog on this issue within the bounds of my current project reviewing the USGS Minerals Yearbooks. This topic is addressed by the United States government in its 1891 publication. Note that “asbestos” was no longer being called “asbestus”.

I cannot explain it any better than did the government, and so let’s just quote what the thought process was in 1891:

“In considering the subject of asbestos care should be taken to distinguish what is properly asbestos and a very similar but distinct mineral, chrysolite. Asbestos is a fibrous species of hornblende, and occurs associated with metamorphic rocks rich in that mineral. Chrysotile, though usually considered in the trade as asbestos, is an entirely different mineral and occurs in distinct veins in serpentine formations. Both minerals are fibrous and both are remarkable for their resistance to the action of heat. The fibers of chrysotile are exceedingly tough, and being at the same time flexible and slightly elastic, it is used principally in the manufacture of fireproof fabrics. Asbestos, on the other hand, while possessing fibers of greater length, has not the same strength, and is used in the manufacture of articles where resistance to heat is requisite but the strength of fiber not essential. The principal uses for which it serves are boiler and steam-pipe covering, packing for fireproof safes, and for making cements and paints.”

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Note that even in the 1890s, the United States was dependent on Canada for its chrysotile fibers. As for the hornblende form of asbestos (what we call amphiboles), they were also used for foundry masks and for firemen, both of whom were exposed to the presence of intense heat.

Interestingly, at least as of 1891, most of the amphibole asbestos fibers mined in the United States came from California and was used in fireproof paint.

There is a lot more to the story of asbestos and asbestiform fibers. The above is a hint on the old ambiguity and how the definition of asbestus, asbestos, and chrysotile have changed over time. That being said, the wording used for any particular fiber does not determine the danger or the need for protection. Rather, let’s stick with good modern science.

Let me know if you have any questions by leaving a comment or emailing me at TheAsbestosBlog@gmail.com. Thank you. Marty