The Mineral WITHERITE
(under longwave UV light)
- Chemistry: BaCO3, Barium Carbonate
- Class: Carbonates
- Group: Aragonite
- Uses: a minor ore of barium and as mineral specimens.
Specimens
Twinning is the result of an error during the growth of the crystal. It occurs when the atomic layer stacking, ABCABCABCABC etc, makes a mistake and a C layer instead of a B layer is place next to an A layer. The result is an ABCABCACBACBACBA stacking. Where the mistake occurs, a mirror plane is produced. If this occurs another time, forming three twins, that are joined in a circle, then a trilling is created. The symmetry of the crystal will appear hexagonal but is still orthorhombic. These crystals can be thought of as a "triple siamese twin" where one crystal takes up one third (or 120 degrees) of the hexagon. Witherite's twins are typically capped with a six sided pyramid and often are dipyramidal.
Witherite is an interesting and valuable collection specimen that anyone, especially a collector of twinned minerals, would love to own.
PHYSICAL CHARACTERISTICS:
- Color is white, colorless, gray, brown, yellowish or greenish.
- Luster is vitreous to dull.
- Transparency crystals are transparent to usually translucent.
- Crystal System is orthorhombic; 2/m 2/m 2/m
- Crystal Habits include a pseudo-hexagonal trilling twin which forms a six-sided prism, usually with a slanted, tapering pyramid. Often they are dipyramidal without any prism faces. The faces are usually striated perpendicularly. Also there are botryoidal, massive and fibrous forms.
- Hardness is 3 - 3.5.
- Specific Gravity is 4.3+ (heavy for transparent minerals)
- Cleavage is distinct in one direction, but not usually seen due to twinning.
- Fracture is uneven.
- Streak is white.
- Associated Minerals include fluorite, celestite, galena, barite, calcite and aragonite.
- Other Characteristics: effervesces in dilute HCl solutions, also fluoresces light blue under both long and short-wave UV light and is phosphorescent under short-wave UV light.
- Notable Occurrences include Cave-in-rock, Rosiclare, Illinois, USA; Alston Moor, Cumberland and Durham, England; Thunder Bay area, Ontario, Canada and Germany.
- Best Field Indicators are twinned habits, reaction to acid, fluorescence and phosphorescent under short-wave UV light and density.
 Amethyst Galleries' Mineral Gallery MINERALS |
WITHERITE specimen wit-1
$ 19.00
$ 19.00
Dims: 1-3/4" x 1-1/2" x 1-1/8"
Wt: 2.12 oz
Cave-In-Rock, Illinois, U.S.A.
This off-white pair of intergrown hexagonal columnar crystals is one of the neater specimens that I have seen come from the Cave-In-Rock locality of Illinois. The crystals seem to be made up of stacked platelets of the mineral, so the prism faces are heavily ridged. They have a dull luster and a rounded, indefinite terminations. A substantial portion of one of the crystals is missing, but seems to have undergone some healing, possibly with calcite or aragonite. As shown in the close-up frame, it is quite fluorescent, giving off a bright blue glow. There is a bit of the calcite/aragonite as a matrix.
wit-1 ($ 19.00)
Cave-In-Rock, Illinois, U.S.A.
WITHERITE specimen wit-2$ 160.00
Dims: 1.8 x 1.5 x 1.1" (4.6 x 3.8 x 2.8 cm)
Wt: 1.17 oz. (33.3 g)
Alma Mine, Hardin County, Illinois, U.S.A.
This small thumbnail specimen contains the finest Witherite crystal that I have seen in my travels. This crystal measures 1.0" (2.5 cm) long and 0.6" (1.5 cm) in diameter and shows no damage that I can see. It has the best hexagonal prismatic form that I have seen in Witherite, and is topped with a steep hexagonal pyramidal termination that is almost perfectly symmetrical. It has a milky-white coloration and a dull pearly-to-vitreous luster, and is very dimly transparent. There is a much smaller crystal laying about 4 mm from the larger one. It is the same in all respects except for its form, which is basically that of a hexagonal bipyramid. The host rock is amorphous and contains shards of a few small, violet fluorite cubes.
wit-2 ($160.00)Alma Mine, Hardin County, Illinois, U.S.A.
WITHERITE specimen wit-3
$ 51.00
$ 51.00
Dims: 2.6 x 2.4 x 1.3" (6.6 x 6.1 x 3.3 cm)
Wt: 6.64 oz. (188.2 g)
Minerva Mine, Hardin County, Illinois, U.S.A.
A thick crust of crystalline Witherite rests on the carbonate-bearing host rock of this specimen. The crust is made up of scores of intergrown pseudohexagonal prismatic Witherite crystals that are generally in good condition and do not exceed 0.6" (1.5 cm) in length. Their form is good considering their intergrowth, with well-defined edges and heavily striated faces that are dull and waxy in luster. All have a color that ranges from a dull cream to gray, and all are translucent and cloudy. A small vein of more massive material extends into one area on the host rock, which looks like a pale brown limestone. A few tiny bits of violet and colorless fluorite rest on the crust, too.
wit-3 ($ 51.00)
Minerva Mine, Hardin County, Illinois, U.S.A.
WITHERITE specimen wit-4
$ 27.00
$ 27.00
Dims: 0.7 x 0.6 x 0.6" (1.8 x 1.5 x 1.5 cm)
Wt: 19.7 g w/ specimen box
Hardin County, Illinois, U.S.A.
This thumbnail specimen consists of a single, moderately warped Witherite crystal that may have started out as two crystals which grew together. This crystal is apparently in excellent condition, as no fresh breakage is visible. Its hexagonal prismatic form is still quite discernable, though some edges are faint and some faces are quite uneven. It has the classic milky-white color and dull waxy-to-matte luster of its species. There is no host rock present. The accompanying documentation did not say so, but I believe that this piece came from the Minerva Mine, the best-known producer of Witherite in the U.S. state of Illinois.
wit-4 ($ 27.00)
Hardin County, Illinois, U.S.A.
WITHERITE specimen wit-6
$ 50.00
$ 50.00
Dims: 1.7 x 1.7 x 1.4" (4.3 x 4.3 x 3.6 cm)
Wt: 4.0 oz. (113.6 g)
Minerva Mine, Hardin County, Illinois, U.S.A.
At least 2 rounded, intergrown clusters of Witherite crystals rest on the white base rock of this specimen. These clusters are very warped and intergrown, so it is difficult to assess their actual dimensions. Each is made up of dozens of small hexagonal prismatic crystals that are generally in very good condition, as only a few are damaged or broken. These crystals are heavily intergrown also, so that one cannot accurately determine their size, but they all have excellent hexagonal prismatic form with well-defined edges, clean faces, and basal terminations. All have a dull cream color and a waxy luster, and are dimly transparent. They glow a dim blue under shortwave ultraviolet light. The clusters actually form a druse that is about 0.4" (1.0 cm) thick which partly covers what appears to be a massive calcite base.
wit-6 ($ 50.00)
Minerva Mine, Hardin County, Illinois, U.S.A.
WITHERITE specimen wit-7
$ 35.00
$ 35.00
Dims: 0.9 x 0.8 x 0.7" (2.3 x 2.0 x 1.8 cm)
Wt: 18.0 g w/ specimen box
Cave-In-Rock, Hardin County, Illinois, U.S.A.
This thumbnail specimen consists of a single Witherite crystal that is heavily intergrown with a broken Witherite base. The crystal has dimensions of 0.6 x 0.6 x 0.6" (1.6 x 1.6 x 1.5 cm), and it is in very good condition- its lack of completeness is not due to damage. Its hexagonal form is excellent, and it takes on the shape of 2 hexagonal pyramidal terminations that have been stuck base-to-base. Its color is a dull, creamy white, and its luster is dull and waxy. The piece is hot-glued into a plastic specimen box.
wit-7 ($ 35.00)
Cave-In-Rock, Hardin County, Illinois, U.S.A.
WITHERITE specimen wit-5
$ 45.00
$ 45.00
Dims: 2.9 x 2.0 x 1.3" (7.3 x 5.0 x 3.3 cm)
Wt: 5.7 oz. (160 g)
Cave-In-Rock, Hardin County, Illinois, U.S.A.
This small cabinet piece consists of a cluster of rounded Witherite prisms that extend from a dull brown base rock. These crystals are generally in good condition, though a few are obviously damaged, and reach dimensions of 0.9 x 0.6 x 0.3" (2.3 x 1.5 x 0.8 cm). Their hexagonal prism is quite good, though all surfaces are heavily patterned, and both surfaces and edges are somewhat curved. They have the classic dull, creamy white color and waxy to pearly luster, and are translucent to dimly transparent. The base is likely made up of limestone, and a few small hollows contain countless tiny dogtooth calcites.
wit-5 ($ 45.00)
Cave-In-Rock, Hardin County, Illinois, U.S.A.