Apophyllite-(KF) (Fluorapophyllite)
Current inventory:  0 gems
 

  
Apophyllite is named from the Greek word apophylliso for away from and leaf, in allusion to the way it exfoliats upon heating.

Discovered in 1800;   IMA status: Apophyllite-(KF) Valid (IMA redefined in 1978)

Chemistry

Chemical Formula:

KCa₄Si₈O₂₀(F,OH) • 8(H₂O)

Hydrated Potassium Calcium Sodium Silicate Fluoride Hydroxide

Molecular Weight:

760.47 gm

Composition:

Potasium

4.37 %

K

5.26 %

K₂O

Sodium

0.45 %

Na

0.61 %

Na₂O

Calcium

21.08 %

Ca

29.50 %

CaO

Silicon

29.55 %

Si

63.21 %

SiO₂

Hydrogen

0.01 %

H

0.12 %

H₂O

Oxygen

42.29 %

O

Fluorine

2.25 %

F

2.25 %

F

- %

F

-0.95 %

-O=F₂

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/H.01-20

Nickel-Strunz 10th Ed. ID:

9.EA.15

9 : SILICATES (Germanates)
E : Phyllosilicates
A : Single nets of tetrahedra with 4-, 5-, (6-), and 8-membered rings

Related to:

Apophyllite Group. Apophyllite-(KF) - Apophyllite-(KOH) Series.

Members of Group:

Apophyllite Group: Apophyllite-(KF), Apophyllite-(KOH), Apophyllite-(NaF), Carletonite

Varieties:

None

Synonyms:

Fluorapophyllite, IMA1976-001

Crystal Data

Crystallography:

Tetragonal - Ditetragonal Dipyramidal

Crystal Habit:

Crystals tabular to prismatic, to 20 cm, commonly pseudocubic with {100}, {001}, and modified by {111}; prism zone deeply striated || [001]; granular.

Twinning:

Rare on {111}.

Physical Properties

Cleavage:

Perfect on {001}, Imperfect on {110}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

4.5 - 5.0

Density:

2.33 - 2.4 (g/cm³)

Luminescence:

Usually none; some specimens may fluoresce pale green or yellow.

Radioactivity:

Barely Detectable; GRapi = 62.81 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Colorless, White, Pink, pale Yellow, Green

Transparency:

Transparent to Translucent

Luster:

Vitreous, Pearly on cleavage {001}

Refractive Index:

1.530 - 1.538  Uniaxial ( + )

Birefringence:

0.0020

Dispersion:

High, may be anomalous

Pleochroism:

None

Occurances

Geological Setting:

A secondary mineral in amygdules or druses in basalts; in cavities in granite; in tactite and other metamorphic rocks; a late-stage hydrothermal mineral in some mineral deposits.

Common Associations:

Calcite, Datolite, Pectolite, Quartz, Zeolites

Common Impurities:

Al, Na

Type Locality:

Lonault and Poona, southeast of Bombay, India

Year Discovered:

1800

View mineral photos:

Apophyllite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

According to the IMA, Apophyllite is not actually a mineral. The IMA no longer recognizes Apophyllite as an official, individual  mineral name but only as the name of a group of minerals. The IMA approved names for these minerals are Apophyllite-(KF), Apophyllite-(KOH) and Apophyllite-(NaF). Some refer to them as Fluorapophyllite, Hydroxyapophyllite and Natroapophyllite respectively. I will continue to refer to these mineral specimens and gems simply as Apophyllite though. Apophyllite-(KF) is by far the most abundant and colorful of the three and is usually what is referred to when a mineral specimen or gemstone is labeled "Apophyllite."

Apophyllite is extremely rare as a gem because it is very brittle and fragile, with an extremely perfect and easy cleavage. Colorless Apophyllite gems are so devoid of any trace of color that they almost appear silvery. The green, iron-rich Apophyllite from India occurs in beautiful crystal groups.

There are many localities worldwide for finding Apophyllite, but exceptional colorless and green crystals are found in the Ahmadnagar, Bombay, Jalgaon, Nasik and Poona Districts, Maharashtra, India.
 

  
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