Taiwan, private collection from Finland.
Actinolite is an amphibole mineral in the tremolite-actinolite series of calcium, magnesium, and iron silicates. Actinolite and Tremolite are two very similar minerals that form a series with each other and essentially share the same chemical formula. Actinolite has a greater presence of iron over magnesium, whereas Tremolite has a greater presence of magnesium over iron. Named in 1794 by Richard Kirwan from the Greek "aktina" (ακτίνα) for "ray" and "lithos" (λίθος) for "stone" in allusion to the fibrous nature of the original specimens.
The green color of Actinolite is produced by the iron in its chemical structure. The amount of iron varies among specimens, causing different contrasts of green. More iron will give a specimen a darker color. Actinolite and Tremolite share several recognized varieties. Mountain Leather, a thickly fibrous and leathery variety, has a silky luster, a soft felt-like feel, and elastic fibers. Nephrite, another fibrous variety, is made up of tough, interlocking fibers, so dense that the fibers are not discernible.
The condition of the sample is excellent. Beautiful, hairlike crystals have bright silvery dark green colour. Age-related wear, fractures and minor cracks may appear. Dirt and dust may exist. Size approx. 8,4cm x 7,1cm x 4,9cm. Weight c. 225g.