THE MINERAL PHILLIPSITE

  • Chemistry: KCaAl3Si5O16 - 6H2O, Hydrated potassium calcium aluminum silicate.
  • Class: Silicates
  • Subclass: Tektosilicates
  • Group: Zeolites
  • Uses: Mineral specimen and chemical filter.
  • Specimens
Phillipsite is one of the rarer zeolites, but is popular among zeolite collectors. It forms interesting aggregates that are commonly clustered into bright white sphericules or balls with a rough crystalline or silky surface. Phillipsite is known to occur as an encrusting precipitate around hot springs. However, phillipsite is more commonly found in the vesicles or bubbles of volcanic rock as are most other zeolites.

Zeolites have an openness about their structure 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 phillipsite can act as a chemical sieve, allowing some ions to pass through while blocking others.

PHYSICAL CHARACTERISTICS:

  • Color is clear, white, yellowish and reddish.
  • Luster is vitreous, also silky on sphericule's surfaces.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include attached crystal aggregates. Single tabular crystals are rare, more commonly twinned into "fourlings" or more complicated groupings. Sphericules are small tight balls that have a sparkling or silky luster in phillipsite. Aggregates can be radiating, fibrous, columnar and encrusting.
  • Cleavage is imperfect in one direction.
  • Fracture is uneven.
  • Hardness is 4 - 4.5.
  • Specific Gravity is approximately 2.2 (very light)
  • Streak is white.
  • Associated Minerals are quartz, calcite, chabazite, natrolite, heulandite, stilbite and other zeolites.
  • Notable Occurrences include Siegerland, Germany; Moyle, Northern Ireland; Capo di Bove and Mt. Vesuvius, Italy; Groschlattengruen, Bavaria; Cape Grim, Tasmania, Australia and Iceland.
  • Best Field Indicators are crystal habit, twinning, density, hardness and associations.
PHILLIPSITE specimens:
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PHILLIPSITE specimen phi-1
$ 65.00
Dims: 2.7" x 2.2" x 1.9"(6.9 x 5.6 x 4.8 cm)
Wt: 4.20 oz.(119.0 g)
Dough Boys Mine, Tasmania, Australia
This is one of the more intriguing zeolite specimens that I have seen. It consists of a crust made up of round clusters of Phillipsite crystals that have a maximum diameter of about 0.4"(1.0 cm) and rise about 0.2"(5 mm) up from their base. Some of the clusters on the specimen's edge are broken, so that one can see a strange trait. Even though the clusters show large, shiny terminations on their surfaces, their cross-sections show round, acicular formations that contain countless radiating, needle-like crystals; these crystals have diameters that are much too small to warrant the size of those terminations. There are two very large(8 mm x 3-5 mm x 2 mm) crystals amidst the clusters. These large crystals are colorless and transparent, whereas the clusters are colored white and are translucent, but all have a vitreous luster on their terminations. The radial material inside the clusters, however, has a silky luster, likely due to the density of the crystals' arrangement. All of the mineral rests on a bed of basalt. This is the first specimen I have seen of this mineral; I believe that it isn't a very common zeolite.
no photo
phi-1 ($ 65.00)
Dough Boys Mine, Tasmania, Australia
PHILLIPSITE specimen phi-2
$ 40.00
Dims: 1.6" x 1.5" x 0.9"(4.1 x 3.8 x 2.3 cm)
Wt: 28.1 g
Dough Boys Mine, Tasmania, Australia
This Phillipsite specimen consists of a crust made up of several white, rounded, intergrown clusters of crystals. The largest of these clusters measures 0.5"(1.3 cm) in dimeter and rises about 0.2"(5 mm) out of the base rock. Some of the clusters on the edge of the specimen are broken, revealing their cross-sections; these cross-sections show the acicular, radiating habits of these crystals. Unlike another specimen that I have seen, these thin crystals seem to have terminations that are proportionate to their thicknesses. There are a few larger, stubby crystals that average about 0.1-0.2"(3-5 mm)in diameter and are colorless and transparent, whereas the round white clusters are translucent. All have a vitreous luster and good form, with very little damage, except for the clusters on the specimen's edge, of course. The crust that this material has formed rests on a base of basalt that contains many loose, round nodules which are paler and more green in color than their matrix. There are also a few rounded, transparent nodules made up either of a different zeolite or, more likely, quartz.
no photo
phi-2 ($ 40.00)
Dough Boys Mine, Tasmania, Australia
PHILLIPSITE specimen phi-3
$ 25.00
Dims: 3.1 x 2.6 x 1.7" (7.9 x 6.6 x 4.3 cm)
Wt: 5.35 oz. (151.6 g)
Horseshoe Dam, Maricopa County, Arizona, U.S.A.
Scores of tiny Phillipsite crystals rest in vugs in the igneous host rock of this speciemen. They are extremely small, not exceeding 0.1" (3 mm) along any axis, and are in excellent condition, due to the protection provided by the hollows in which they rest. They are difficult to study even with a 10-power loupe, but appear to occur either in tiny, rounded compact sprays or as druses of tiny crystals. The more exposed rounded sprays have a cream coloration, whereas the druses have a much cleaner white color. The dull brown host rock on which they rest is very rough and heavily pitted with hollows, most of which contain Phillipsite.
no photo
phi-3 ($ 25.00)
Horseshoe Dam, Maricopa County, Arizona, U.S.A.
 

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