Apophyllite Group Information about the mineral specimens or Crystals

COMPOSITION:
The Apophyllite group is layered with alternating silicate sheets and the potassium,
sodium, calcium, fluorine and water layers. But unlike other phyllosilicates, the Apophyllite Group silicate sheets are composed of inter connected four and eight member rings. This is what gives these minerals their typical tetragonal or pseudo-tetragonal symmetry. Only Apophyllite Group members have this unique inter connected four and eight member ring structure. It seems apophyllite is not a mineral, but rather a general term for a group of
three official minerals that are similar in their chemistry and physical properties. And a
fourth mineral Carletonite.

NATRO- APOPHYLLITE NaCa4 Si8O20F - 8H2O Tetragonal;
quite rare and its typical brown color can help distinguish it from its close cousins.

HYDROXY- APOPHYLLITE KCa4 Si8O20(OH, F) - 8H2O Tetragonal
relatively common, but specimens typically lack any color and are limited to pseudo-cubic crystal habits

FLUOR- APOPHYLLITE (K, Na)Ca4 Si8O20(F,OH) - 8H2O Orthorhombic (pseudo tetragonal)
the most abundant and colorful of the three and is usually what is referred to when a specimen is just labeled apophyllite.

CARLETONITE KNa4Ca4(CO3)4Si8O18 (F, OH) - H2O Tetragonal
a rare silicate mineral that is so far found in only one location. Mont Saint-Hilaire, Quebec, Canada.

ENVIRONMENT:
Apophyllite specimens are found in ancient lava and basalt flows and are usually associated with zeolites. The crystals grow in cavities, called amygdules or vesicles, that were 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.

CRYSTAL DESCRIPTION:
Almost always as well formed individual crystals, varying from the common, short prismatic habit that has four sided prisms (with square cross sections) truncated with either a steep
four sided pyramid or a pinacoid termination or both. Simple, blunt, square prisms develop
if the pyramids are missing. Rarely are the prisms missing, but if they are, crystals could also appear octahedral because of the four sided pyramids. The faces of the pyramids do not line
up 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.

TESTS:
Fuses easily, bubbling and swelling to a white vesicular enamel. The depths of the mass fluoresce weak greenish white after heating.

DISTINGUISHING CHARACTERISTICS:
Normally colorless or white. The different (pearly) luster on the basal face distinguishes apophyllite from any cubic mineral it might otherwise suggest. The typical square pyramid
and prism combination with the two lusters is easy to recognize. In case of doubt, the basal cleavage makes the identity certain. Distinguished from stilbite and heulandite by lesser swelling, quicker melting with boiling, and the usual fluorescence after heating

LOCALITIES:
The traprocks of Paterson, New Jersey, and the Bay of Fundy. Produce the typical, well
formed white crystals. By far Apophyllite's most impressive color is the pastel green color found in theDeccan Traps (ancient basalt flows) in India. These are most prominent near Poona. Mont Saint-Hilaire, Canada, has the rare blue Carletonite. There are many other locations here in the USA. Such as Arizona, Michigan, Oregon; Pennsylvania and North Carolina. Other localities include Japan, Britain, Many Nordic countries and Brazil.

USES:
Some crystals of apophyllite are cut as gemstones. But most crystals are used by collectors
as mineral specimens.

FACTS & HISTORY:
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.

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