About
Apophyllite was originally regarded as a single mineral, with a variable ratio of fluorine to hydroxyl. In 1978, the IMA sub-classified into two distinct minerals: Fluorapophyllite and Hydroxyapophyllite. In 1981, an additional rare member with sodium replacing the potassium was added to the group, and called Natroapophyllite.
In a controversial move, the IMA has recently changed the scientific naming of these minerals for easier cataloging and alphabetical indexing. The new mineral names are Apophyllite-(KF) [instead of Fluorapophyllite], Apophyllite-(KOH) [instead of Hydroxyapophyllite], and Apophyllite-(NaF) [instead of Natroapophyllite]. Although use of the original names is now discouraged by the IMA, these names are still used and referenced, with the new names frowned upon by many collectors. The reality is that most collectors rarely sub-classify Apophyllite specimens, and simply label them all as Apophyllite.
Apophyllite-(KF) is the most common and abundant of the group. Most specimens labelled simply as "Apophyllite" are of the Apophyllite-(KF) form. Apophyllite-(KOH) is less common, but is still the dominating form of Apophyllite in several localities, including most of the Virginia occurrences. Apophyllite-(NaF) is very rare, and is found sparingly at only a few localities.
Apophyllite almost always occurs together with zeolites, especially in traprock environments. Apophyllite appears very similar to the zeolites, and is sometimes even confused with them. However, the physical structure of Apophyllite is different, with tetrahedrons aligning in sheets as a phyllosilicates, as opposed to the zeolites which are tectosilicates.
Carletonite is a rare blue mineral that is similar to Apophyllite, and it only occurs in Mont Saint Hilaire, Quebec, Canada. Many classify Carletonite as group member within the Apophyllite group.
Apophyllite is named from a combination of the Greek word "apo" - to be off, and "phyllos" - leaf, alluding to the property of this mineral that it exfoliates (flakes apart like a leaf) when heated due to loss of water in its structure.
Crystal Forms & Aggregates
(Note: Apophyllite-(KF) and Apophyllite-(KOH) both crystallize in the tetragonal crystal system, whereas Apophyllite-(NaF) crystallizes in the orthorhombic system.)
Other ID Marks
Complex Tests
Striking Features
Environment
Uses
Noteworthy Localities
A classic locality that produced highly-desirable pink Apophyllite crystals is St. Andreasberg, Harz Mountains, Lower Saxony, Germany. In Africa, good crystals of Apophyllite-(KOH) come from the Wessels Mine and N'Chwaning Mines in the Kalahari Manganese Fields of South Africa.
In the U.S., New Jersey has produced the best Apophyllite in several important localities. The Upper New Street Quarry, Paterson; and nearby Prospect Park, both in Passaic Co., are known for their exceptional well-formed crystals, usually white in color. Equally important is the Millington Quarry, Somerset Co., which has produced crystals and platy aggregates with outstanding luster. Very good Apophyllite crystal plates and drusy forms were also extracted in the diabase seams of Laurel Hill (Snake Hill), Secaucus; and Bergen Hill, both in Hudson Co.
Exceptional Apophyllite of the (KOH) type have come from the Fairfax Quarry, Centreville, Fairfax Co., Virginia. Druzy microcrystals associated with blue Kinoite have come from the Christmas Mine, Gila Co., Arizona.
Common Mineral Associations
Distinguishing Similar Minerals
Heulandite - Different crystal form.
Calcite - Different crystal form, has lower hardness.
Photos
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