THE MINERAL EDINGTONITE

  • Chemistry: BaAl2Si3O10 - 4H2O, Hydrated Barium Aluminum Silicate.
  • Class: Silicates
  • Subclass: Tectosilicates
  • Group: Zeolites
  • Uses: As mineral specimens and chemical filters.
  • Specimens
Edingtonite is another example of the variety offered in the Zeolite Group of minerals. Like so many other zeolites, it is not a surprise to see that edingtonite is typically found in the cavities of volcanic rocks. Although not a colorful mineral, it does form some nice well-shaped crystals. It is an unusual mineral in that it has two polytypes or two phases that are not yet recognized as separate minerals. One type has a little more water content and a has an orthorhombic symmetry. The other type has a tetragonal symmetry. Both types have an overall tetragonal look to their crystals.

Edingtonite's structure has a typical zeolite openness that allows large ions and molecules to reside and actually move around inside the overall framework. The structure actually 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 edingtonite can act as a chemical sieve, allowing some ions to pass through while blocking others.

Edingtonite is one of only two zeolites to have barium in its chemistry. The other one is harmotome, with a formula of BaAl2Si6O16 - 6H2O. The heavy barium ion gives edingtonite the highest density of any zeolite. The larger amounts of water and the lower barium ion ratio lowers harmotome's density in relation to edingtonite.

PHYSICAL CHARACTERISTICS:

  • Color is colorless or white.
  • Luster is vitreous to dull.
  • Transparency: Crystals can be transparent but most commonly are just translucent.
  • Crystal System is tetragonal and orthorhombic.
  • Crystal Habits include blocky to prismatic or bladed crystals usually with a square cross-section, also massive.
  • Cleavage is perfect in one direction lengthwise.
  • Fracture is uneven.
  • Hardness is 4
  • Specific Gravity is approximately 2.8 (average, although heavy for a zeolite).
  • Streak is white.
  • Associated Minerals are manganite, heulandite, natrolite, stilbite and other zeolites.
  • Notable Occurrences include Ice River, Canada; Old Kilpatrick, Scotland and Bohlet, Sweden.
  • Best Field Indicators are crystal habit, density and associations.
EDINGTONITE specimens:
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EDINGTONITE specimen edg-1
$ 225.00
Dims: 2.8" x 2.6" x 1.7" (7.1 x 6.6 x 4.3 cm)
Wt: 6.26 oz. (177.6 g)
Ice River, British Columbia, Canada
This specimen's host rock is at least 40% covered with a cluster made up of hundreds of small, white Edingtonite crystals. They measure no longer than 0.3" (8 mm) and are generally in excellent condition, showing a small amount of damage. Close examination of the crystals reveals their tetragonal prismatic crystal form which is topped by wedge-like terminations whose contact edges are truncated by two secondary faces, giving the appearance of four-sided pyramids. They have a white color and a pearly luster, and are translucent to nearly transparent. There is an interesting spot on the cluster that I believe shows where it came into contact with the face of a rhombohedron- the depression in the cluster is in the shape of a partial rhombus, and there is a tiny bit of calcite stuck in one corner. This cluster coats a base that consists of another single, large rhombohedral calcite crystal that is heavily damaged but still has definite form. It is a dull, off-white color and is translucent with a pearly luster.
no photo
edg-1 ($225.00)
Ice River, British Columbia, Canada
EDINGTONITE specimen edg-2
$ 130.00
Dims: 2.9" x 1.8" x 1.6" (7.4 x 4.6 x 4.1 cm)
Wt: 3.94 oz. (111.9 g)
Ice River, British Columbia, Canada
A crust made up of scores of small, white Edingtonite crystals coats the crystalline calcite host rock of this specimen. The Edingtonite crystals are in very good condition, with damage mostly limited to the crystals along the crust's edge. They do not exceed 0.2" (5 mm) in length and their tetragonal prismatic form is well-defined. They have a white color and a pearly luster, and range from translucent to nearly transparent. The calcite that acts as their base is in the form of a few intergrown rhombohedral crystals that show considerable damage. Some of the calcite has a brighter color than most of it, and almost appears to be striated, but it is definitely calcite, and has probably taken on the tendencies of a mineral that was adjacent to it.
no photo
edg-2 ($130.00)
Ice River, British Columbia, Canada
EDINGTONITE specimen edg-3
$ 32.00
Dims: 1.4" x 0.9" x 0.8" (3.6 x 2.3 x 2.0 cm)
Wt: 15.6 g
Ice River, British Columbia, Canada
This thumbnail specimen consists of a crust of tetragonal prismatic Edingtonite crystals that partly covers a crystalline calcite base. These crystals do not exceed 0.1" (3 mm) in any dimension, and show very good form and only a small amount of damage. They have a milky-white color and a pearly-to-vitreous luster, and are translucent. The calcite base on which they rest is rounded, but shows definite rhombohedral forms. The crystals are a dull yellow color and are translucent and cloudy.
no photo
edg-3 ($ 32.00)
Ice River, British Columbia, Canada
EDINGTONITE specimen edg-4
$ 90.00
Dims: 2.0 x 1.4 x 0.8" (5.0 x 3.6 x 2.1 cm)
Wt: 1.7 oz. (48 g)
Ice River, British Columbia, Canada
This hand specimen consists of a crust of tightly arranged Edingtonite crystals that rest on a crystalline calcite base. These Edingtonites are generally in very good condition and reach about 5 mm in length. All have excellent orthorhombic prismatic form and have the standard white color and pearly luster of the specie. They are all translucent and cover most of the calcite base.
no photo
edg-4 ($ 90.00)
Ice River, British Columbia, Canada
 

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