THE SCHUNDLER COMPANY
Confusion and Publicity about Vermiculite and Asbestos
There has been a lot of publicity during the last year or two about vermiculite and asbestos, and a lot of confusion as a result. Briefly stated, the problem goes back to a very real problem at what had been one of the largest vermiculite mines in America which was closed in 1990.
Commercially available vermiculites today are virtually free of any asbestos (like our South African vermiculite), or they contain only insignificant amounts similar to other products that are naturally occuring, mined, processed, and used throughout the industrial world today. To read more about this subject, click on any one of the following pages:
Origins and Characteristics....
Vermiculite is a member of the phyllosilicate group of minerals, resembling mica in appearance. It is found in various parts of the world, but currently the major mines are located in South Africa, China, Brazil, Zimbabwe, and the United States. The largest mine today is located in the Palabora region of North-Eastern Transvaal in South Africa. It's vermiculite is basically a hydrated phlogopite mica which has the remarkable ability to expand to many times its original volume when heated---a property known as exfoliation.
TYPICAL PHYSICAL PROPERTIES
TYPICAL PHYSICAL PROPERTIES OF EXFOLIATED VERMICULITE
| Color: | Light to dark brown |
| Shape: | Accordion-shaped granule |
| Bulk density (a): | 64-160 kg/cu m
4-10 lb/cu ft |
| Moisture loss@110 °C (230 °F): | 4-10% |
| pH (in water): | 6-9 |
| Combustibility: | Non-combustible |
| Sintering temperature: | 1150-1250 °C
2100-2280 °F |
| Fusion point: | 1200-1320 °C
2200-2400 °F |
| Cation exchange capacity (b): | 50-150 me/100g |
| Specific heat: | 0.84-1.08 kJ/kgK
0.20-0.26 kcal/kgK
0.20-0.26 Btu/lb F |
| Waterholding capacity (a): | 220-325% by wt
20-50% by vol |
THERMAL CONDUCTIVITY AT DIFFERENT BULK DENSITIES
| Bulk densities | Thermal conductivity values |
| kg/cu m | lb/cu ft | Lambda W/mK | Btu in/sq ft h °F |
| 56-64 | 3.5-4.0 | 0.058 | 0.40 |
| 80-96 | 5.0-6.0 | 0.064 | 0.44 |
| 160-192 | 10-12 | 0.071 | 0.49 |
TYPICAL SIZES, DENSITIES, AND NAMES OF EXPANDED VERMICULITE*
|
SIZES | DENSITIES | GRADES OR SIZES |
| MM | IN | N/A | KG/M 3 | LB/FT 3 | U.S.SYSTEM
VA and SC Mines | ASTM GRADE
DESIGNATIONS | INTERNATIONAL
and South African |
| 16 | 5/8 | DOWN | 56-72 | 3.5-4.5 | N/A | 0-Premium | Premium (6) |
| 8 | 5/16 | DOWN | 64-85 | 4.0-5.0 | 1 | 1-Large | Large (4) |
| 4 | 5/32 | DOWN | 72-90 | 4.5-5.5 | 2 | 2-Medium | Medium (3) |
| 2 | 0.08 | DOWN | 75-112 | 4.7-7.0 | 3 | 3-Fine | Fine (2) |
| 1 | 0.04 | DOWN | 80-144 | 5.0-9.0 | 4 | 4-Superfine (if VA or SC) *
or
3-Fine (if South African) * | Super Fine (1) |
| 0.5 | 0.02 | DOWN | 90-160 | 5.6-10.0 | 5 | 4-Superfine | Micron (0) |
*Note: In the United States, the ASTM Grade Designationd for Vermiculite (as outlined in ASTM C-516) have problems in the descriptions of fine and superfine grades. The South African "Superfine (1)" is too coarse to conform with the ASTM Grade "4-Superfine". Both the South African Fine and Superfine Grades conform to the ASTM designation for "Fine Grade". And during the last few years the American grade 4-Superfine and a grade 5 seem to be getting smaller and smaller so as to be more and more like the South African Micron, or smaller. To be sure, it's not a perfect world!
NOTE:These sizes and values are given for general information purposes only. The Schundler Company does not necessarily produce all these grades, and uses grades which may not conform to these specifications at all times.
For more information about vermiculite, you might want to look at:
The Vermiculite Home Page
Our basic, more generic page about vermiculite.
Vermiculite Statistics and Information
(http://minerals.usgs.gov/minerals/pubs/commodity/vermiculite/index.html
(published by the United States Geological Survey)
or look through the rest of our website, or call or contact us at:
The Schundler Company
10 Central Street
Nahant, MA 01908
(ph)732-287-2244
www.schundler.com
email: info@schundler.com
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