Amphibole refers to a group of dark-colored silicate minerals that is typically composed of iron and magnesium ions. Actinolite is a member of this group and it forms a series with Tremolite. When groups of minerals form a series that means they have an identical crystal structure. However, they differ in the elements that are contained in that structure. Actinolite has a larger amount of iron, while Tremolite has a larger amount of magnesium.
What Does Actinolite Asbestos Look like?
Actinolite asbestos is green because of the large amount of iron in its crystal structure. However, the iron content in individual specimens varies, with those having the most iron being the darkest green.
This form of amphibole asbestos is sometimes found as a thin, splinter-like inclusion inside Quartz crystals. That is an indication that the actinolite fibers were trapped inside the Quartz as it was forming. If the inclusions run parallel to each other and are dense, they will cause what mineralogists refer to as chatoyancy in the Quartz. What this means is that the actinolite will reflect a narrow band of light across the center of the Quartz crystal.
There are several known varieties of actinolite:
- Mountain Leather is thick and fibrous, with a silky look, soft to the touch and elastic fibers
- Byssolite is composed of tiny fibrous crystals that look like a mass of hair
- Nephrite is also fibrous, with tough fibers that interlock and are so dense that the individual fibers cannot be seen. Translucent Nephrite has a uniformity of color and is extremely tough. It is classified as Jade.
Both actinolite and tremolite are composed of movable and elastic fibers that are extremely brittle. However, actinolite asbestos is less common than tremolite. Actinolite can also occur in groupings that appear to radiate like wheat shafts, or as thin masses that look like bunches of hair. Actinolite fibers are extremely acid-resistant.
Where is Actinolite Asbestos Found?
Outside of the United States, actinolite can be found in several locations in Europe. Byssolite is present in Knapperwand and the Untersulzbach Valley in Austria. Actinolite included in Quartz and Byssolite are prevalent in the Val D’Aosta, Italy. However, the best quality actinolite comes from Norway. Lower Silesia, Poland has great quantities of Nephrite.
In addition to Europe, actinolite is found in Canada, Namibia and Pakistan.
Inside the U.S., actinolite sites include the:
- Carlton Quarry in Vermont
- French Creek Mine in Pennsylvania
- Keystone Quarry in Pennsylvania
- Calumet Mine in Colorado
- Sears Creek Mine in Washington
There are several Nephrite deposits in this country including the:
- Granite Mountains in Wyoming
- Jade Mountain Mine, the Shungnak River Mine and the Dahl Creek Mine in Alaska
- Bagby Mine, the Jade Cove Mine and the Willow Creek Mine in California
How Was Actinolite Asbestos Used?
Owing to the fact that actinolite asbestos is rare, it was not widely used commercially. What little usage was made of it was as a component of building materials.