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Roger Weller, geology instructor

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Apophyllite
by Jeong Park
Physical Geology
Fall 2009
     

                                                         Apophyllite

                                                                                Apophyllite is KF.Ca4(Si2O5)4.8H2O

 

What is Apophyllite?
 

     Apophyllite, whose name roughly means "to leaf apart" in Greek, is a mineral classic. It was given its name because crystals tend to peel or flake apart when they are heated due to the loss of water molecules. Apophyllite is composed of hydrated potassium calcium silicate, and forms tabular crystals of cubic or octahedral structure, occasionally exhibiting the bipyramidal formations. Pictures below are an apophyllite tip in different dictions from my personal collections.

 

Pictures by Jeong Eun Park
 

THE OFFICIAL APOPHYLLITES

MINERAL

FORMULA

SYMMETRY

COLOR RANGE

TYPE LOCALITY

FLUORESCENCE

FLUOR-
APOPHYLLITE

(K, Na)Ca4
Si8O20(F,OH) - 8H2O

Tetragonal;
4/m 2/m 2/m

White, colorless, green, yellow or violet

Not named

Some specimens fluoresce pale green or yellow

HYDROXY-
APOPHYLLITE

KCa4
Si8O20(OH, F) - 8H2O

Tetragonal;
4/m 2/m 2/m

White or colorless

Ore Knob Mine, Jefferson, North Carolina

Non-fluorescent

NATRO-
APOPHYLLITE

NaCa4
Si8O20F - 8H2O

Orthorhombic;
2/m 2/m 2/m (pseudo-
tetragonal)

brown, brownish yellow, yellow or colorless

Sampo Mine, Takahashi, Okayama, Honshu, Japan

Non-fluorescent

 

Table from http://www.galleries.com/minerals/silicate/apophyll/apophyll.htm

     Fluorapophyllite is by far the most abundant and colorful of the three and is usually what is referred to when a specimen is just labeled apophyllite. Hydroxyapophyllite is also relatively common, but specimens typically lack any color and are limited to pseudo-cubic crystal habits.

     The natroapophyllite is quite rare and is found at only a few localities. Its typical brown color can help distinguish it from its close cousins. Natroapophyllite, by virtue of its more significant chemical and symmetrical difference, is truly a distinct mineral.

     Fluorapophyllite and hydroxyapophyllite however are a different story. The two are different minerals only because of the difference in the percentage of fluorine to hydroxyl ions. They represent the end members of a series that could be called the apophyllite series. The name apophyllite persists however and its usage is widespread, especially when distinguishing the true identity of specimens is difficult. Most mineral guide books list apophyllite as a single mineral and the rest of this discussion will deal with apophyllite in general.

     Apophyllite typically associated with green translucent prehnite that forms a rolling carpet on top of which are scattered sparkling clear pseudo-cubic apophyllite crystals, making very attractive specimens. Kinoite from the Christmas Mine in Arizona is a beautiful blue color and is often coated in tiny sparkling apophyllite crystals. Apophyllite is commonly associated with exceptional quartz and calcite crystals as well.

Other Names for Apophyllite

Synonyms:

Apofillite

Brünichite

Brünnichite

Brünnikite

Fisheye Stone

Ichthyophthalme

Ichthyophthalmite

Leucocyclite

Mesoype

Oxhaverite

Oxheverite

Pyramidal Zeolite

Tesselite

 

 

 

 

The physical characteristics of Apophyllite

Chemistry: (K,Na)Ca4Si8O20(F,OH) - 8H2O, Hydrated Potassium Calcium Sodium Silicate Fluoride Hydroxide.

Class: Silicates

Subclass: Phyllosilicates

Group: Apophyllite

Uses: Only as mineral specimens.

Color: clear, white, green, yellow, pink, violet or rarely brown.

Luster: vitreous to pearly on cleavage surfaces.

Luster is Transparency: Crystals are transparent to translucent.

Crystal System: tetragonal; 4/m 2/m 2/m; natroapophyllite is orthorhombic, 2/m 2/m 2/m.

Crystal Habits: include four sided prisms (with a square cross-section) truncated with either a steep four sided pyramid or a pinacoid termination or both. If the pyramids are missing, the crystals can look cubic. Rarely are the prisms missing, but if they are, crystals could appear octahedral because of the four sided pyramids. The faces of the pyramids do not lineup with the prism faces but with their edges, therefore the pyramid faces have four edges and appear diamond shaped instead of triangular like the pyramid faces of quartz. Rare tabular hydroxyapophyllite crystals are also known.

Cleavage: perfect in one direction (basal).

Fracture: uneven.

Hardness: 4.5 - 5.

Specific Gravity: approximately 2.3 - 2.4 (lighter than most translucent minerals).

Streak: white.

Other Characteristics: Prism faces are striated lengthwise, some specimens are fluorescent and crystals will flake when heated.

Associated Minerals: prehnite, quartz, heulandite, stilbite, natrolite, analcime, datolite, babingtonite, cavansite, calcite, idocrase, wollastonite, kinoite, gyrolite and many other zeolites.

Green Apophyllite

  

Pictures Credited to John Van Rees/exquisitecrystals.com from http://www.exquisitecrystals.com/Apophyllite-p-2-c-47.html

Apophyllite Cluster

    

Pictures Credited to John Van Rees/exquisitecrystals.com from http://www.exquisitecrystals.com/Apophyllite-p-1-c-47.html

 

 

Where is Apophyllite found?
 

     Apophyllite specimens are found in ancient lava and basalt flows. The crystals grow in the now solid cavities, called amygdules or vesicles, formed by air bubbles when the rock was molten. Apophyllite is also found in the voids in the contact metamorphic zone limestones that surround intrusive rocks. Notable Occurrences are extensive and include the Deccan Traps (ancient basalt flows) in India especially around Poona, also found in Christmas Mine, Arizona; Fairfax, Virginia; Upper Peninsula, Michigan; Oregon; Pennsylvania; Paterson, New Jersey and North Carolina, USA; Rio Grande do Sul, Brazil; Isle of Skye, Scotland; Collinward, Northern Ireland; Mexico; Nova Scotia and Mont Saint-Hilaire, Canada; Iceland; Kongsberg, Norway; Harz Mountains, Germany and Sampo Mine, Takahashi, Okayama, Honshu, Japan.
 

Various Apophyllites
 

Photos Credited to R.Weller/Cochise College

 

Why Apophyllite are so famous to collectors?

     Although not that well-known by the general public, apophyllite is quite popular among mineral collectors. It is probably the first exotic mineral that a young collector will own after filling up on specimens of calcite, quartz, pyrite, galena, mica, fluorite, gypsum, apatite, etc. After these common minerals, apophyllite seems like a real rarity and it offers so much to the collector. It has beauty, pastel colors, a bright luster, interesting well formed habits, unusual associations with other exotic minerals and recently large amounts of quality specimens have become available at amazingly low prices compared to twenty years ago. What makes apophyllite so popular among collectors is its fantastic crystals with their gem-like vitreous to pearly luster.

The highest quality apophyllite, will exhibit a translucent pearly sheen on the shaft of the crystal formation and transparent, vitreous prism faces. This gem quality apophyllite has unusual & startling clarity throughout most of the points.
 

Picture from http://www.satyacenter.com/store/crystal/apophyllite/1348

 

Gem Apophyllites
 


 

From the right, “Apophyllite Pyramid Tower” pictures from http://www.satyacenter.com/store/crystal/apophyllite/418

“Big Points Michael Druzy Cluster” pictures from http://www.satyacenter.com/store/crystal/apophyllite/3484

“Green Apophyllite Cluster in Calcite Oyster Shell” pictures from http://www.satyacenter.com/store/crystal/apophyllite/2774

“Pale Green Apophyllite Pyramids Cluster on Peach Stilbite Mound” pictures from http://www.satyacenter.com/store/crystal/apophyllite/2773

“Fluorite Phallus in Calcite Matrix” pictures from http://www.satyacenter.com/store/crystal/apophyllite/2772
 

Other use of Apophyllite

     Some people believe apophyllite has energy to heal. Often, people use it as a calming and tranquil agent which encourages honesty to self and others. They believe that apophyllite is excellent in stressful situations, and for clearing negative thought patterns because it creates a conscious connection between the physical and the spiritual realm, and it acts as an excellent transmitter for vibrational energy, and so enhances healing work. Moreover, they believe, an apophyllite cluster makes an excellent space clearer when apophyllite is placed in a room. These concepts of a healing crystal are very interesting.   

 

 

 

Work Sited

http://www.galleries.com/minerals/silicate/apophyll/apophyll.htm

http://www.mindat.org/min-283.html

http://franklin-sterlinghill.com/palache/apophyllite.stm

http://webmineral.com/data/Apophyllite.shtml

http://www.mythnlynx.com/Apophyllite.html

http://www.satyacenter.com/store/crystal/apophyllite

http://www.exquisitecrystals.com/Apophyllite-p-2-c-47.html