THE MINERAL SCOLECITE
- Chemistry: CaAl2Si3O10-3H2O, Hydrated calcium aluminum silicate
- Class: Silicates
- Subclass: Tectosilicates
- Group: Zeolites
- Uses: mineral specimen and chemical filter
Specimens
Scolecite's structure has a typical zeolite openness about it that allows large ions and molecules to reside and actually move around inside the overall framework. The structure contains open channels that allow water and large ions to travel into and out of the crystal structure. The size of these channels controls the size of the molecules or ions and therefore a zeolite like scolecite can act as a chemical sieve. Scolecite's structure contains aligned chains of silicate tetrahedrons. This produces the needle-like crystals and the cleavage results from the weaker bonds between the chains.
Scolecite, a calcium zeolite, natrolite, a sodium zeolite, and mesolite, a calcium and sodium zeolite, are closely related and sometimes found together. The presence of calcium in two of the minerals slightly alters the structure from that of natrolite; from an orthorhombic symmetry to a monoclinic symmetry. However, twinning of scolecite and mesolite often make them look orthorhombic All three minerals are referred to as "chain" or "needle" zeolites. They are similar and hard to distinguish when in clusters with radiating, acicular habits. Natrolite tends to forms thin crystals with pyramidal terminations, but mesolite's fibrous crystals are usually the thinnest crystals of the three minerals. Scolecite's larger crystals tend to be more robust and durable. These characteristics are only generalities and can not be used as dependable identifying traits. Absolute identification can not be made by ordinary means.
PHYSICAL CHARACTERISTICS:
- Color is clear or white.
- Luster is vitreous to silky.
- Transparency: crystals are transparent to translucent.
- Crystal System is monoclinic; 2/m
- Crystal Habits include sprays of thin acicular crystals with slanted terminations. Also occurs in radiating fibrous clusters.
- Cleavage is perfect in two directions, prismatic. Cleavage is hard to see due to small crystal size.
- Fracture is conchoidal.
- Hardness is 5.
- Specific Gravity is approximately 2.2 (very light)
- Streak is white.
- Associated Minerals are quartz, apophyllite, babingtonite, heulandite, stilbite and other zeolites.
- Notable Occurrences include Poona, India; Riverside Co., California; Iceland; Skye Scotland and Santa Catarina, Brazil.
- Best Field Indicators are crystal habit, hardness, density and associations.
 Amethyst Galleries' Mineral Gallery MINERALS |
SCOLECITE specimen sco-1$ 80.00
Dims: 2.8" x 2.5" x 2.9"(7.1 x 6.4 x 7.4 cm)
Wt: 5.75 oz.(163.2 g)
Maharashtra State(near Amadnagar), India
The beauty in this specimen not only comes from the Scolecite on this specimen, but from its surroundings, too. The Scolecite is present in the form of several small sprays of tiny white needles, and one large acicular, radiating cluster that resembles an okenite "puffball". I don't know if the crystals on the cluster have been damaged, but many seem to be laying perpendicular to the direction of growth... Oh, well. The aspect of this specimen that likely gives it such value is the fact that the cluster and the sprays of Scolecite rest on a concentrated bed of exceptional fluorapophyllite crystals! These crystals are all a pale green, well-formed with minimal damage, and quite transparent. They have the standard vitreous luster and tetragonal prismatic crystal form, with basal terminations that are truncated by angled secondary faces. They seem to average between 1/4 and 1/2" in length, and there are several of them. It's gorgeous!
sco-1 ($ 80.00)Maharashtra State(near Amadnagar), India
SCOLECITE specimen sco-2
$ 80.00
$ 80.00
Dims: 2.1 x 2.0 x 1.4" (5.3 x 5.1 x 3.6 cm)
Wt: 1.12 oz. (31.9 g)
Kolar, India
This beautiful, delicate specimen consists of a spray of radiating Scolecite needles. These needles achieve a maximum length of 1.9" (4.8 cm) and do not exceed 2 mm in thickness. Though many of the crystals on the outer edges of the spray are broken and incomplete, most of them are intact and in excellent condition. Their thin monoclinic prismatic form is excellent, as all edges are well defined and all faces are smooth and possess a bright pearly-to-vitreous luster. Though the crystals are colorless and transparent as individuals, their interference with each other in the spray makes them appear milky white and translucent. The spray was separated from its host at its base, so there is no other material present.
sco-2 ($ 80.00)
Kolar, India
SCOLECITE specimen sco-4$ 160.00
Dims: 4.7 x 3.5 x 2.2" (11.9 x 8.9 x 5.6 cm)
Wt: 10.49 oz. (297.6 g)
Kolar, India
Three clusters of radiating Scolecite needles rest on the green apophyllite base of this hand specimen. The largest cluster shows considerable damage which likely occurred during mining, but the specimen is otherwise in very good condition. The Scolecite crystals reach lengths of nearly 1.5" (3.8 cm) and have excellent monoclinc prismatic form, with well-defined edges and striated but clean faces that possess the standard pearly luster. Individual crystals are colorless and transparent at their terminations, but the lower thirds of their lengths appear to be milky-white and opaque due to a thin coating that I cannot identify. Several smaller Scolecites that are separate from the larger clusters hold up a few small, pseudocubic apophyllites (see the close-up image), and all rest on a base that is made up of a few large, broken apophyllites that have a pale green coloration and a rather dull luster.
sco-4 ($160.00)Kolar, India
SCOLECITE specimen sco-5
$ 60.00
$ 60.00
Dims: 3.2 x 1.3 x 0.9" (8.1 x 3.3 x 2.3 cm)
Wt: 23.6 g
Kolar, India
This small hand specimen consists of two intersecting sprays of radiating Scolecite needles. The smaller of the two sprays has a visible length of less than 0.5" (1.3 cm), whereas the larger spray measures 3.4" (8.6 cm) in length. This larger spray shows moderate damage in the form of broken crystals, and is generally in good condition. The crystals therein have excellent monoclinic needle-like form, with well-defined edges and striated but clean faces. They are colorless, transparent, and reasonably clear- though they tend to take on a cloudy translucence near their base- and possess the standard bright pearly luster.
sco-5 ($ 60.00)
Kolar, India
SCOLECITE specimen sco-6
$ 110.00
$ 110.00
Dims: 2.4 x 1.8 x 1.6" (6.1 x 4.6 x 4.1 cm)
Wt: 1.30 oz. (37.1 g)
Jalgaon, India
A single spray of Scolecite needles or blades makes up the bulk of this large thumbnail specimen. It is in moderately good condition, showing considerable damage in the form of broken crystals, which reach a maximum length of no more than 2.2" (5.6 cm). The crystals themselves appear to have a rather warped, flattened monoclinic form. They possess the standard pearly luster and a milky-white coloration that renders them dimly transparent at best. They are accompanied by a few bright green apophyllites that have good form and a few broken bits of laumontite crystals. There is no base or host rock, however.
sco-6 ($110.00)
Jalgaon, India
SCOLECITE specimen sco-7
$ 37.00
$ 37.00
Dims: 2.9 x 2.2 x 1.5" (7.4 x 5.6 x 3.8 cm)
Wt: 6.93 oz. (196.5 g)
Bombay, India
This small hand specimen consists of a basalt vug inside of which rest two rounded Scolecite clusters. These clusters are in excellent condition due to the protective nature of their surroundings and exceed no more than 0.5" (1.3 cm) along any axis (they are somewhat ovate in form). Each cluster is made up of countless tiny Scolecite needles that do not exceed 0.2" (5 mm) in length. Each is at least as thin as a human hair, and so cannot be effectively studied without high magnification. However, I believe that their monoclinic needle-like form is probably good. Individual crystals are colorless, transparent, and likely clear, though the cluster is essentially white in color. Each needle also has a pearly luster that gives the clusters a dull sparkle. The hollow in which they rest appears to be coated with a crust of almost microcrystalline quartz.
sco-7 ($ 37.00)
Bombay, India
SCOLECITE specimen sco-8
$ 115.00
$ 115.00
Dims: 3.3 x 2.2 x 1.4" (8.4 x 5.6 x 3.6 cm)
Wt: 4.00 oz. (113.5 g)
Kolar, India
At least 4 clusters of radiating Scolecite needles are intergrown to form this specimen. These clusters are in excellent condition, showing little damage, and each contains dozens of Scolecite needles that do not exceed 0.8" (2.0 cm) in length. These needles have excellent monoclinic form and have a pearly luster. As individuals, they are colorless, transparent and moderately clear, but the clusters are essentially white and translucent at best. A small amount of basalt serves as the base, and several small apophyllites are present.
sco-8 ($115.00)
Kolar, India
SCOLECITE specimen sco-9
$ 140.00
$ 140.00
Dims: 3.6 x 3.1 x 2.6" (9.0 x 7.9 x 6.7 cm)
Wt: 8.7 oz. (247 g)
Kolar, Nasik-Poona Rd., Maharashtra State, India
This cabinet specimen basically consists of a large cluster of hundreds of Scolecite needles that extends from a stilbite base. These needles reach lengths of about 2.5" (6.4 cm) and are generally in good condition, showing light damage. Their monoclinic form appears to be good, and they range from colorless to milky-white and transparent to translucent. All have the standard bright pearly luster. The stilbite base on which the cluster rests is definitely crystalline, but the crystals are almost completely obscured by the Scolecite- a small amount of basalt is attached. The piece can be stood erect, and is rather stable in this position.
sco-9 ($140.00)
Kolar, Nasik-Poona Rd., Maharashtra State, India
SCOLECITE specimen sco-10
$ 54.00
$ 54.00
Dims: 3.4x1.4x0.6" (8.7x3.6x1.6cm)
Wt: 0.24oz. (6.7g)
Poona, India
This is a nice specimen of scolecite. It presents very well, having a tall cluster of crystals with a cluster of smaller crystals affixed about 1/3 of the way up. The largest crystals do not have terminations, but some of the smaller ones do. All of the scolecite is colorless, with transparency obscured by numerous internal fractures. Close examination shows that the crystal surfaces have scores of very tiny crystals, slightly dulling the luster. The specimen looks good when backlit, as the individual crystals show up better that way.
sco-10 ($ 54.00)
Poona, India