ACTINOLITE
Specimen act-18

Dims: 3" x 1-3/4" x 1-1/4"

Wt: 3.1 oz

Calumet Iron Mine, Salida, Chaffee Co., Colorado, U.S.A.

I've seen a few of these specimens before; this is an example of a variety of Actinolite known as Uralite. Uralite is attractive to me because it looks completely fibrous! The entire specimen is composed of the material. The base is a gray color with a hint of green, and looks like compressed fibrous needles that go in random directions, whereas the crystals that grow out of the base seem to be composed of the same compact, fibrous groups of needles that all go into the same direction, and were compressed into crystalline shapes. They occur in long, thin prisms that appear almost pseudotetragonal; the angled basal terminations give it away upon close examination, though. I like this- it makes me think of asbestos that someone pressed into a complex mold!

Dims: 8-7/8" x 5-1/2" x 2-1/2"

Wt: 3.1 oz

Hwy. 28 roadcut @ Hardwood Lake, Raglan Township, Renfrew Co., Ontario, Canada

Judging from the locality description, I'll wager that it would be easy to find out exactly where this specimen came from! There are dozens of Actinolite crystals on a base of another olivine-related material. These crystals show some heavy damage in some areas, but several are in surprisingly good condition, with complete terminations that themselves have a pretty, silky luster. One can just catch the translucence of some of the more exposed crystals, which can achieve lengths of 1 inch. It's a large piece that is somewhat "spread out", and quite thin in spots.

Dims: 3" x 1-3/4" x 1-1/4"

Wt: 3.1 oz

Calumet Iron Mine, Salida, Chaffee Co., Colorado, U.S.A.

A variety of Actinolite that is known as Uralite makes up this specimen. Most of these that I have seen come from the Calumet Iron Mine, and this one is no exception. It consists of a matrix of massive Uralite, on which are growing hundreds of tiny needlelike prisms of the mineral. They have a pseudotetragonal form with a basal termination that is slightly angled. The crystals all have a gray-green coloration and a fibrous appearance if viewed under a high-power loupe or a microscope. Their luster is pearly to waxy in appearance and there is noticeable damage to a substantial number of the crystals.

Dims: 2.7" x 2.4" x 2.3" (6.9 x 6.1 x 5.8 cm)

Wt: 10.41 oz. (295.3 g)

Calumet Iron Mine, Salida, Chaffee Co., Colorado, U.S.A.

This Actinolite specimen, consisting of a variety that is called Uralite, has crystals that are larger than most that I have seen on similar pieces. The largest complete crystal measures 0.5 x 0.2 x 0.1" (1.3 x 0.5 x 0.3 cm), and several incomplete crystals have measurements larger than that. They occur in a monoclinic prismatic form that appears almost pseudotetragonal, but the basal terminatoins are slightly angled. All have a light greenish-gray coloration and a rather silky luster. Close examination of the crystals shows that they seem to be made up of very thin, compact, parallel fibers that have been aggregated into a prismatic form. This "aggregation" gives the material its silky sheen. Needless to say, it is opaque. Almost the entire specimen is composed of Actinolite, either crystalline or massive, but there does seem to be a tiny bit of white quartzite visible, and one small, clear quartz crystal does rest among some of the Actinolites.

Dims: 3.0" x 2.1" x 1.4" (7.6 x 5.3 x 3.6 cm)

Wt: 3.02 oz. (85.6 g)

Calumet Iron Mine, Salida, Chaffee Co., Colorado, U.S.A.

Scores of tiny Actionolite crystals rest on one face and in several crevices that extend into the host rock of this specimen. The crystals are small, not reaching more than 2 mm in length and 1 mm along either of the other axes. There is some visible damage due to crushing, but the crystals are generally in good condition. Their monoclinic prismatic form is rather difficult to study due to their size, but all appear to be well-formed. They have a gray-green color and a pearly luster, and individually, they are translucent, but their size and concentration makes this difficult to determine. The host rock out of which they extend is made of massive Actinolite, and actually appears to consist of crystals that are so tightly intergrown that they have lost almost all semblance of individuality!

Dims: 3.6 x 2.8 x 1.5" (9.1 x 7.1 x 3.8 cm)

Wt: 6.3 oz. (177.9 g)

Santa Catalina Island, Los Angeles County, California, U.S.A.

This hand specimen consists of a chunk of heavily-intergrown Actinolite crystals. All are either broken or are too heavily intergrown to be complete, but some reach lengths of almost 2.5" (6.4 cm). Their crystal form is definable, but as I have stated, none are complete. They have a grayish-green coloration and a pearly luster, and are essentially opaque, though some of the thinner and more exposed edges may be dimly translucent.

Dims: 4.2 x 3.0 x 2.0" (10.7 x 7.6 x 5.1 cm)

Wt: 14.5 oz. (410 g)

Vermont, U.S.A.

A compact mass of intergrown Actinolite needles comprises this specimen. These needles are generally broken, incomplete and are difficult to study due to their compact nature. They appear to have a reasonably good monoclinic form, given their intergrowth, and their nearly olive-green coloration and pearly luster are standard for the species. There is no host rock present.

Dims: 1.8 x 1.7 x 1.6" (4.5 x 4.2 x 4.0 cm)

Wt: 1.9 oz. (54 g) w/ base

Alchuri, Shigar Valley, Baltistan, Northern Areas, Pakistan

The Actinolite on this specimen was not documented, and it took some study for me to realize that the matte of green needles was not elbaite, as I originally thought. There are hundreds, if not thousands, of these needles resting on the piece, and most appear to be in good condition. They do not tend to exceed 0.4" (1 cm) in length, and they have a flattened, elongated form that is common for this specie. All have a gray-green color and a vitreous luster and are transparent and quite clear. They are heavily interspersed through the white base rock, and many are included in a single quartz crystal that extends from the base material. The piece is hot-glued onto an acrylic base.

Dims: 4.1 x 2.9 x 2.5" (10.3 x 7.5 x 6.4 cm)

Wt: 1 lb., 8.3 oz. (688 g)

CT Pit No. 3, Marin County, California, U.S.A.

This large, rounded cabinet specimen consists of a chunk of compact, crystalline Actinolite. The crystals that make up the piece are extremely intergrown but still often distinguishable as single units. Though none are intact and complete, their monoclinic form is evident and sometimes well-defined. The Actinolite has a uniform dark green color and a bright pearly luster, and is dimly translucent.

Dims: 3.3 x 2.3 x 1.6" (8.4 x 5.8 x 4.1 cm)

Wt: 7.3 oz. (208 g)

Guerneville, Sonoma County, California, U.S.A.

This cabinet piece seems to be a partial rounded nodule of crystalline Actinolite. As the crystals are heavily intergrown, there are no actually complete ones visible on the piece. Intergrowth makes it difficult to study their individual forms, but there are some blades visible with appreciable monoclinic form; some of these reach nearly 1.5" (3.8 cm) in length. Their color is dark green with a hint of blue and their luster is pearly-to-vitreous. Portions of individual crystals are also appreciably transparent, though heavily fractured and included. There is no host rock present, and the rounded nature of the piece suggests that it may have undergone water-wear.

Dims: 3.4 x 2.3 x 1.5" (8.5 x 5.8 x 3.9 cm)

Wt: 6.8 oz. (194 g)

Guerneville, Sonoma County, California, U.S.A.

This cabinet piece is made entirely out of intergrown or aggregated Actinolite blades. Therefore, none of these blades are complete. All show monoclinic form where visible and all have the standard dull, deep green color and vitreous luster. Their intergrowth also makes determination of translucence impossible. There is no host rock present.

Dims: 4.1x3.0x3.1" (10.5x7.6x8.0 cm)

Wt: 17.9 oz. (506g)

Avren, Bulgaria

This specimen is primarliy composed of unusually large, long prismatic crystals of actinolite, heavily intergrown and cemented together by talc crystals. Many of the actinolite crystals are clearly hexagonal in cross section, and there is no hint of a fibrous structure. The crystals are dimly translucent, although there are some areas clear enough that green highlights reflect from internal fractures. The largest actinolite crystal measures at least 80mm in length and 13mm in width.

Dims: 5.7x4.4x2.0" (14.5x11.3x5.0 cm)

Wt: 39 oz. (1.1kg)

Swarthout Canyon, San Gabriel Mountains, San Bernardino County, California, USA

This specimen consists of hundreds of intergrown green actinolite crystals with some talc crystals providing contrast. There are no true crystal faces, as all surfaces appear to be cleavage or fracture surfaces. Still, the exposed crystals are rather large, and the specimen is pleasing in appearance due to the luster of these crystals and their random orientations.

Dims: 3.81x2.70x1.69" (9.67x6.87x4.30cm)

Wt: 11.35oz (321.1g)

Avren, Rhodope Mountains, Bulgaria

This hand specimen is composed of clusters of green actinolite crystals growing into a mass of talc crystals. It is clear that the actinolite lined a cavity and talc crystals filled the space not occupied by actinolite. The talc is unusually crystalline and is a nearly silvery white in color. While the actinolite appears dark green and opaque, under a loupe or bright light, the transparency of thin sections and small crystals is apparent.

Dims: 5.87x4.36x2.46" (14.90x11.07x6.24cm)

Wt: 44.52oz (1260g)

Swarthout Canyon, San Gabriel Mountains, San Bernardino County, California, USA

This cabinet specimen of actinolite is nearly pure, although it appears that fractures in the specimen have filled with quartz veins. The actinolite is green with a vitreous luster, and the individual crystals are translucent. The specimen is comprised of many intergrowths of radial clusters of crystals, and while most surfaces are show a splintery fracture, there are a few distinct crystals that show excellent form. There are other minerals present - I think I can recognize some biotite crystals. The specimen is rather fragile - some crystals flake off during handling.

Dims: 4.61x3.64x2.39" (11.71x9.24x6.08cm)

Wt: 29.68oz (840g)

Swarthout Canyon, San Gabriel Mountains, San Bernardino County, California, USA

This is a good specimen of actinolite. While most of the surfaces are cleavage, there are a number of natural crystal surfaces including some that show striations, and a few crystals have terminations. These crystals have the usual green color, and the intergrown clusters result in an appealing crystal appearance. In places, the clusters are separated with areas of white talc crystals which have the characteristic pearly luster and soapy feel, and in at least one protected pocket distinct crystals are visible (silvery-white lamellar masses).

Dims: 4.52x2.90x1.27" (11.48x7.37x3.23cm)

Wt: 13.22oz (274g)

Swarthout Canyon, San Gabriel Mountains, San Bernardino County, California, USA

This is another nearly pure actinolite specimen. The crystals are well-formed, and while most surfaces are cleavage or fracture, there are some natural terminations and faces. These crystals look nearly transparent, have a dark mossy-green color, and a vitreous luster. There are several areas with a spall amount of quartz visible, plus there are some tiny black crystals present, probably biotite. This specimen is rather fragile - tiny green crystals easily flake off.

Dims: 4.24x2.59x2.25" (10.77x6.59x5.71cm)

Wt: 15.90oz (450g)

Swarthout Canyon, San Gabriel Mountains, San Bernardino County, California, USA

On one side of this actinolite specimen there are many small areas exposing talc crystals between the actinolite. The talc is a creamy white, perhaps with a hint of green, and has the characteristic greasy feel. The actinolite is generally green, dimly translucent, and the crystal fibers give it a nearly silky luster. Some of the crystals are nearly transparent, a deeper green, and show natural crystal form and terminations. These crystals are generally surrounded with talc.

Dims: 3.76x1.68x1.29" (9.54x4.27x3.28cm)

Wt: 7.27oz (206g)

Swarthout Canyon, San Gabriel Mountains, San Bernardino County, California, USA

This specimen came to us from the same mine as the other Swarthout Canyon specimens, but it looks different - it must have come from a different area of the mine. There is no hint of talc or quartz, and the lighter areas appear to be more actinolite, perhaps less pure. Also, there are areas of rust staining. Some of the actinolite crystals are quite transparent, at least when viewed with a loupe, and these have an excellent green color. Also, several sprays of actinolite crystals clearly radiate from a point - it is clear that the specimen is an intergrowth of several radial clusters.