NATROLITE
Specimen nat-15

Dims: 2.25" x 1.5" x 1.5"(5.7 x 3.8 x 3.8 cm)

Wt: 1.80 oz.(51.0 g)

Clear Creek, San Benito County, California, U.S.A.

Though these Natrolite crystals come from a well-known locality for this particular mineral, there are a few aspects of them that strike me as odd. First, their general size and proportions: these crystals are short, stubby, and thick! Second, they are eight-sided; there are 4 main prism faces and 4 secondary faces between each main face. Finally, they are generally a milky white color, with only the largest crystal showing any good transparency. They rest on a base of what appears to be a basalt that shows some decay. This host rock also serves as a matrix for several other pieces of embedded natrolite- one can see small examples of Natrolite's good cleavage in this rock. I don't know if this form is standard for San Benito specimens, but I certainly wasn't expecting it!

Dims: 2.5" x 1.5" x 0.9" (6.4 x 3.8 x 2.3 cm)

Wt: 27.4 g

Springfield Butte, Lane, Oregon, U.S.A.

A crust of Natrolite coats the thin, brown, igneous host rock of this specimen. The crust is made up of round clusters of thousands of radiating Natrolite needles. These needles do not exceed 0.3" (8 mm) in length and are at least as thin as human hair. A small area on one edge of the crust shows some damage in the form of crushed crystals, but most are in excellent condition. Their luster appears to be pearly and they appear to be colorless and transparent as individuals, but their concentration makes them appear white. They are far too small for one to accurately study their crystal form, unless high-powered magnification is used.

Dims: 2.0 x 1.5 x 0.8 (5.1 x 3.8 x 2.0 cm)

Wt: 1.06 oz. (30.1 g)

Springfield Butte, Springfield, Lane County, Oregon, U.S.A.

This large thumbnail consists of a small, brown igneous base rock that is partly covered by a crust made up of hundreds or perhaps thousands of radiating, needle-like Natrolite crystals. The crust averages approximately 0.3" (8 mm) thick and is in excellent condition, showing crushed and broken crystals only at its edges. Individually, the crystals are colorless and clear, but their tight clustering makes them appear to be essentially white. It is impossible to study their orthorhombic form without magnification, but they likely have clean, flat faces, as the crystals generally possess a bright, pearly-to-vitreous luster. A few areas on the Natrolite "crust" show some rust-staining, and a portion of it is covered with at least 30 tiny calcite crystals. These crystals do not exceed 2 mm in diameter and are in excellent condition. Their rhombohedral form is very good, and all have a faintly milky color and are dimly transparent. Their color and clarity may be caused by their visual surface texture, which gives them a utterly dull matte luster.

Dims: 1.7 x 0.6 x 0.4" (4.3 x 1.5 x 1.0 cm)

Wt: 6.0 g w/ base

Mt. Ste. Hilaire, Quebec, Canada

This small specimen consists of a cluster of long, prismatic Natrolite crystals that extend off of the edge of a small crust. These crystals achieve lengths of up to 1.5" (3.8 cm) and are generally in excellent condition; only two show any obvious breakage, and these are not easily noticeable. The crystals have very good orthorhombic form, with moderately well-defined edges and clean though heavily striated faces. The prism faces are quite dull due to their striations and have a dull pearly-to-waxy luster, whereas the termination faces are quite clean and possess a bright vitreous luster. The Natrolites have a rather dull, pale-gray coloration that appears to be caused by the inclusion of a dark substance. This color deepens very slightly towards the base of the cluster, and renders the crystals translucent to dimly transparent, whereas they would nominally be quite transparent. However, they all appear to contain substantial internal fracturing, which also provides interference. The crust off of which the cluster grows is coated with scores of tiny Natrolites that have a much darker gray coloration. These needles to not exceed 2 mm in length, and are thus not easy to see without magnification. The specimen arrived to us glued onto a square acrylic base, and I believe that it is too delicate to separate it.

Dims: 1.3 x 1.3 x 0.6" (3.3 x 3.3 x 1.5 cm)

Wt: 14.0 g

Springfield Butte, Springfield, Lane County, Oregon, U.S.A.

This thumbnail consists of a crust of Natrolite that covers a thin slab of basalt host rock. The crust is made up of several intergrown, round clusters of radiating Natrolite needles. These crystals do not exceed 0.3" (8 mm) in length, and are at least as thin as human hair, and probably thinner. They are certainly too thin for one to effectively study their orthorhombic form. However, they do reflect light with a bright pearly luster off of their faces. Individually, they are likely colorless and transparent, but packed together in the crust, they are essentially a milky-white color and translucent. The basalt rock on which they rest has a few nodules of more massive Natrolite trapped within.

Dims: 2.3 x 1.5 x 1.2" (5.8 x 3.8 x 3.0 cm)

Wt: 1.9 oz. (52.4 g)

Cape Grimm, Tasmania

This large thumbnail specimen consists of two partly-intersecting clusters of radiating Natrolite needles. These clusters are generally in very good condition, showing a relatively small amount of damage with respect to their delicacy. The crystals that make up the cluster do not exceed 0.5" (1.3 cm) in length or 2 mm in either width or depth. All have excellent orthorhombic form, with well-defined edges and clean faces that possess a pearly luster on their prism faces and a brighter, vitreous luster on their termination faces. All are milky-white in coloration, though they are a bit dirty, and are quite translucent. There are several small, very odd crystals accompanying the Natrolite- I would guess that they are made of analcime, as they do not react to acids as calcite would, and some have a rather good trapezohedral form. They have a brown coloration on their outer surfaces, but a few are broken and reveal milky-white-to-colorless cores.

Dims: 2.6 x 2.0 x 0.7" (6.6 x 5.1 x 1.8 cm)

Wt: 1.3 oz. (36.2 g)

Springfield Butte, Springfield, Lane County, Oregon, U.S.A.

Another large thumbnail specimen, this piece consists of a layer of fibrous, radiating Natrolite that covers one side of a thin, quartz-coated basalt slab. The Natrolite crystals are in excellent condition and reach lengths of 0.3" (8 mm) on average. They are far too thin for one to effectively study without high magnification, but their form is likely very good. All have a milky-white coloration and a pearly luster, and though individual crystals would likely be noticeably transparent, they are essentially only dimly translucent at best when clustered. Resting among the needles are many small calcite crystals whose dimensions range from less than 1 mm square to 0.2 x 0.1 x 0.1" (5 x 3 x 3 mm). The larger crystals have a double-terminated scalenohedaral form, whereas the smaller crystals form is rhombohedral (see the close-up image). All have a milky-white coloration and a dull waxy luster, and are translucent.

Dims: 2.1 x 1.9 x 1.6" (5.3 x 4.8 x 4.1 cm)

Wt: 1.85 oz. (52.6 g)

Mount Saint Hilaire, Quebec, Canada

This large thumbnail specimen is made up mostly of Natrolite, in the form of sprays of stubby prismatic crystals. The largest of these crystals reaches 0.5" (1.3 cm) in length and at least 0.1" (3 mm) in diameter, but is mostly covered by sprays of smaller crystals. Though a few are obviously damaged, most appear to be in excellent condition. Their othorhombic prismatic form is very good, with well-defined edges and generally clean faces, though some of the larger crystals appear to be slightly warped. All have a milky white coloration and a pearly-to-silky luster, and are translucent. There does not appear to be any host rock present- the crystals grew off of a base of semicrystalline Natrolite.

Dims: 2.4 x 2.0 x 1.3" (6.1 x 5.1 x 3.4 cm)

Wt: 2.3 oz. (64 g)

Rudniy, Kazakhstan

Many intergrown clusters of radiating Natrolite needles partly cover the base of this large hand specimen. These needles are generally in excellent condition, as the clusters show little damage, and reach lengths of at least 0.2" (5 mm). Though they are tightly arranged and too fine to study with a loupe, they likely have excellent orthorhombic form. All have a pale, creamy-orange color and a pearly luster, and are likely at least partly transparent near their terminations. They are accompanied by many scattered bits of orange chabazite that appear to have some evidence of crystalline tendencies, though not much. All of this rests on a base of what appears to be gray, crystalline calcite.

Dims: 1.1 x 0.7 x 0.5" (2.7 x 1.9 x 1.3 cm)

Wt: 8 g

Clear Creek, near New Idria Mine, California, U.S.A.

This thumbnail piece consists of a large partial Natrolite crystal. This crystal is in fair condition, showing considerable damage, and has a fair orthorhombic prismatic form- though its prism faces are relatively well-defined, no termination exists. It has a milky-white color and a dull pearly luster, and is highly translucent. It shows some rust-staining, but there is no host rock present.

Dims: 3.9 x 3.1 x 2.5" (9.8 x 7.8 x 6.4 cm)

Wt: 12.4 oz. (352 g)

Prospect Park, New Jersey, U.S.A.

Several sprays of radiating Natrolites rest on the base of this large cabinet piece. These crystals reach at least 0.5" (1.3 cm) in length and are generally in very good condition, though there is some visible damage to some clusters. They show excellent orthorhombic form and have a milky-white color and a pearly, almost silky luster. All are translucent, and many are dimly transparent. They are accompanied by several clusters of pale green prehnite nodules, and some calcite epimorphs that may have formed around now-decayed Natrolite. This is a rather "busy" piece.

Dims: 3.0 x 2.1 x 1.5" (7.7 x 5.4 x 3.8 cm)

Wt: 4.2 oz. (119 g) w/ base

Wasson's Bluff, near Paarsboro, Nova Scotia, Canada

Scores of lovely Natrolite prisms ring the stilbite-rich base of this cabinet piece. These crystals reach up to 1" (2.5 cm) in length, though usually only about 0.4" (1.0 cm) of each is visible. They are generally in excellent condition and have excellent orthorhombic prismatic form. Their milky-white color and pearly-to-vitreous luster are standard for the specie, and many are at least partly transparent. A large amount of stilbite or more, compact, fibrous Natrolite makes up the bulk of the base of this specimen, though a small amount of basalt is present. An acrylic stand is attached.

Dims: 2.6 x 1.9 x 1.7" (6.6 x 4.7 x 4.3 cm)

Wt: 4.1 oz. (116 g)

Flinders, Victoria, Australia

Crusts of fibrous Natrolite line the larger hollows in the basalt base of this small cabinet piece. These needles do not exceed 0.2" (5 mm) in length and are very fine, but are generally in excellent condition due to the protective nature of the hollows. They likely have excellent orthorhombic form, and are colorless and transparent as individuals. Their luster is likely vitreous. Smaller nodules within the host rock contain massive or warped crystals of analcime. A card that came with this piece states that at one time it was part of the National Collection of Victoria, Australia.

Dims: 3.2 x 3.1 x 2.1" (8.0 x 7.9 x 5.2 cm)

Wt: 7.9 oz. (224 g)

Weldborough Quarry, North East Tasmania, Australia

A few hollow vesicles in the basalt host of this cabinet specimen are lined with small, fine Natrolite needles. These needles do not generally exceed 0.1" (3 mm) in length and are in excellent condition. Though too fine to study without high magnification, they likely have excellent orthorhombic form. All are colorless and transparent as individuals, and show a vitreous luster. Some of the other hollows in the host rock are lined with tiny quartz druses, and others are completely filled with apparently massive analcime.

Dims: 0.4x0.4x1.3" (1.1x0.9x3.4 cm)

Wt: 0.1 oz. (2.6g)

Mt. St. Hilaire, Quebec, Canada

This is a fine thumbnail specimen of natrolite. It is primarily a single large transparent and colorless crystal with a good termination. The surface is covered with lengthwise striations and other crystal growth patterns, hiding the actual excellent transparency of the crystal. There is a basal fracture about halfway up the crystal (cleavage would be smooth - this flaw looks conchoidal).