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Apophyllite Photolitherland.jpg
Category Phyllosilicate
(repeating unit)
Crystal system Tetragonal; (Apophyllite-(NaF) is orthorhombic)
Color Usually white, colorless; also blue, green, brown, yellow, pink, violet
Crystal habit Prismatic, tabular, massive
Cleavage Perfect on (001)
Fracture Uneven
Mohs scale hardness 4.5 - 5
Luster Vitreous; pearly
Streak White
Diaphaneity Transparent to translucent
Specific gravity 2.3 – 2.4
Refractive index 1.536
Pleochroism Dichroic (colorless)
References [1]

The name apophyllite refers to a specific group of phyllosilicates, a class of minerals. Originally, the group name referred to a specific mineral, but was redefined in 1978 to stand for a class of minerals of similar chemical makeup that comprise a solid solution series, and includes the members apophyllite-(KF), apophyllite-(KOH), and apophyllite-(NaF). The name apophyllite is derived from the Greek ἀπόΦυλλίςο apophylliso, meaning "it flakes off", a reference to this class's tendency to flake apart when heated, due to water loss. These minerals are typically found as secondary minerals in vesicles in basalt or other volcanic rocks. A recent change in the nomenclature system used for this group was approved by the International Mineralogical Association, removing the prefixes from the species names and using suffixes to designate the species.[2]

Though relatively unfamiliar to the general public, apophyllites are fairly prevalent around the world, with specimens coming from some of the world's most well-known mineral localities. These localities include: Jalgaon, India; the Harz Mountains of Germany, Mont Saint-Hilaire in Canada, and Kongsberg, Norway, with other locations in Scotland, Ireland, Brazil, Japan, and throughout the United States.


Faceted Apophyllite, 0.60 ct, from India

Apophyllites are popular as collector's minerals. This popularity is due to a combination of factors, including their abundance, color variety, and well-defined crystals. Naturally forming pyramidal structures, they refract light in obvious rainbows, and can form "natural pyramids" when subjected to rock tumbling.

Species of Apophyllite[edit]

  • Fluorapophyllite-(K) (formerly fluorapophyllite, apophyllite-(KF)), KCa4Si8O20(F,OH)·8H2O - white, colorless, yellow, green, violet[3]
  • Hydroxyapophyllite-(K) (formerly hydroxyapophyllite, apophyllite-(KOH)), KCa4Si8O20(OH,F)·8H2O - white, colorless[4]
  • Fluorapophyllite-(Na) (formerly natroapophyllite, apophyllite-(NaF)), Na4Si8O20F·8H2O - brown, yellow, colorless[5]


  • MinDat Listing
  • Mineral Galleries
  • Colville AA, Anderson CP, Black PM (1971). "Refinement of the crystal structure of apophyllite: I. X-ray diffraction and physical properties". American Mineralogist. 56: 1222–1233.