Vermiculite from a New York Home ca 1945 (C) InspectApedia Munn & Steel & Mica-Fil Vermiculite Building Insulation
Vermiculite identification photos, hazards, history, advice

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Vermiculite insulation produced or sold by Munn & Steele or Mica-Fil Brands:

Does Munn & Steele vermiculite insulation contain asbestos? What about Mica-Fill vermiculite insulation? How are Mica-Fil or Munn & Steele vermiculite products identified, & what should be done about potential vermiculite-asbestos hazards ascribed to this vermiculite insulation?

This article series explains how to recognize vermiculite building insulation that may contain asbestos fibers. This article permits visual identification of vermiculite insulation; we include our own as well as US EPA photographs of various forms of vermiculite insulation to assist in recognizing vermiculite in buildings. We provide photographs and descriptive text of asbestos insulation and other asbestos-containing products to permit identification of definite, probable, or possible asbestos materials in buildings.

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Munn & Steele Vermiculite Insulation, Siscoe Vermiculite Mines, & Mica-Fill Vermiculite Insulating Products

Reader Question: did Munn & Steele Vermiculite Insulation Contain Asbestos?

Vermiculite from a New York Home ca 1945 (C) InspectApedia Vermiculite from a New York Home ca 1945 (C) InspectApedia

I read your in depth article on vermiculite on the web. We began a DYI Reno on our bathroom (1945 row house in ... NY we just purchased) and came across a product in the ceiling closely resembling the vermiculite on your site. I have checked extensively on line and cannot find the manufacturer on the bag, meaning if it is asbestos or not.

The company is Munn & Steele and the bits of paper on the backing we could read had the words or partial words of Zonolite, mineral and Munn&Steele with a Newark NJ address. What I have read is that not all zonolite has asbestos and the product coming from the Libby mine are asbestos. What I cannot find is if this particular company was ever a reseller or manufacturing of the Libby asbestos product or if they just used the term zonolite in their own micafil product.

The paper is brown and the Munn lettering is in black with red, while the Zonolite is in a light blue and the word mineral is in black lettering. The paper looks old - Like from the 40's or 50's. We stopped the clean up after a contractor we bought in to access the rebuild of the bathroom pointed out that he thought it was asbestos. The substance is flaky and shiny. Do you have any info? I tried to download the image file in the EPA site of samples of bags if Zonolite but the file can't be opened for some odd reason.

Reply: history of Munn & Steele's Vermiculite & the Siscoe Vermiculite Mines

John R.Munn, from an old Newark New Jersey family, was chairman of Munn & Steele Inc., makers of building insulation material, including vermiculite insulation.

I could not find the company's vermiculite insulation, and it's possible it was a re-branded material from the most-common source (the Libby mine whose vermiculite did contain asbestos).

However to be clear, not all vermiculite sold in the U.S. came from Libby - just most of it.

Interesting, there was a relationship between Munn & Steele and a different vermiculite source: the Siscoe Vermiculite mines[1] located in Quebec. Without a detailed review of the court records, we don't know if there was a product use or only a trademark issue. Munn & Steele were a party in a much-cited 1957 trademark trafficking dispute with the Siscoe Vermiculite mine [3] whose vermiculite was also sold under the trade name "MIca-Fil" [2]

Some of the vermiculite citations for Siscoe dated back to the 1940's and extended at least through the 1950's.

At this juncture we can't know for sure just what vermiculite mine sources were used when by various vermiculite insulation marketing companies as the principals are too-long gone to ask.

My search for records indicating whether or not Munn & Steele actually used vermiculite that came from the Libby mine (or from the Siscoe mine) did not find any indicators suggesting a yes or no answer.

You know from your reading that not all vermiculite sources contain asbestos. I add that one cannot determine asbestos content in vermiculite by normal visual inspection. Polarized light microscopy (PLM) procedures are needed.

Interestingly the Siscoe vermiculite mine was a subsidiary of the Siscoe gold mine of which more was written. Sources I found cite vermiculite mines in southeast Ontario and in Quebec and possibly in the Gowganda Ontario area where cobalt was of principal mining interest. Some sources report asbestos in the Gowganda area so unless your tests find no asbestos in your vermiculite I would treat it as PACM _ presumed asbestos containing material.

In 1959 Siscoe, principally interested in gold mining, sold its two wholly-owned vermiculite interests to a building supplier, Sidney Roofing & Paper Company Ltd. [7].

Since the most-asbestos-contaminated vermiculite in the U.S. came from the Libby Montana mine, that would have been a different source. Much (but probably not all) of the Libby Montana vermiculite was sold under the brand Zonolite.

If you can send me some sharp photos of your vermiculite and of any packaging or markings that would be very helpful.

With all that interesting and useless detail I have to add that even though your vermiculite may contain asbestos we just don't know unless you have a test performed. If you want to do that (please keep me informed) the cost is typically around $50. US. and you can find a lab at ASBESTOS TESTING LAB LIST

What to Do About Your Vermiculite Insulation

The best way to minimize your risk of amphibole asbestos exposure is to avoid disturbing vermiculite-based insulation in any way. If vermiculite-based insulation is contained and not exposed to the home or interior environment, it poses very little risk. - Health Canada

See the following

References for the discussion above

Reader follow-up:

From historical documents and I did see a Trademark infringement blurb in my search. I was as equally stumped in finding where their product could have been mined. I did locate another reference to a mas-Celo operation that was suspended in the late 30's and came back on line in the early 40's. From looking at pictures on line we have a lot of black colored substances that more mirror the micafil than the zonolite.

I was not able to locate any records denoting an affiliation with the WR Grace Libby mine or if the Grace zonolite mined and sent to the Hamilton refinery was ever sold to Munn for redistribution. Maybe I dodged a big one. My architect said it is not vermiculite but he took a sample to have it tested. I will keep you posted and we have ceased all work.


Your architect is almost certainly mistaken - your photos show what is rather unmistakable vermiculite loose fill insulation.

But "vermiculite" does not necessarily mean "asbestos" as we've been discussing. Only a lab test can determine that question.


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