Apophyllite, 5.72 cts. Photo © Joel E. Arem, PhD, FGA. Used with permission.
Although not suitable for jewelry, apophyllite is a popular collector’s piece. Perhaps the whitest of all gems, some cut specimens are so devoid of color they can appear almost silvery. This stone is not rare, but facetable material is quite scarce.
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| Data | Value |
|---|---|
| Name | Apophyllite |
| Crystallography | Tetragonal. Crystals pseudo cubic; tabular, prismatic, sometimes pyramidal. Rare fluorapophyllite-(Na) crystalizes in the orthorhombic system. |
| Refractive Index | 1.530-1.540 |
| Colors | Colorless, white, grayish, pale yellow, pale green, dark green, pink, reddish. |
| Luster | Vitreous, pearly on cleavage. |
| Hardness | 4.5–5 |
| Wearability | Display Only |
| Fracture | Uneven |
| Specific Gravity | 2.3-2.5 |
| Birefringence | 0.003 to 0.001 or less. May appear isotropic. |
| Cleavage | Perfect 1 direction; easy |
| Luminescence | None |
| Luminescence Present | No |
| Enhancements | Surface coatings, radiation, heating. |
| Typical Treatments | Heat Treatment, Irradiation, Surface Coating |
| Transparency | Transparent to opaque |
| Absorption Spectrum | Not diagnostic |
| Formula | KCa4Si8O20(F, OH)· 8H2O |
| Pleochroism | None |
| Optics | o = 1.53-1.54; e = 1.53-1.54 (variable). Optically (+) or (-); uniaxial. See “Identifying Characteristics” below. |
| Optic Sign | Uniaxial +, Uniaxial - |
| Etymology | From the Greek words apo and phyllos, “away from” and “leaves,” describing the gem's tendency to exfoliate when strongly heated. |
| Occurrence | Secondary mineral in basic igneous rocks, such as basalts and traprocks. |
Apophyllites on matrix, Fengjiashan Mine (Daye Copper mine), Edong Mining District, Daye Co., Huangshi Prefecture, Hubei Province, China. © Rob Lavinsky, www.iRocks.com. Used with permission.
The gemstones known as apophyllites belong to a solid solution series of minerals that includes fluorapophyllite-(K), fluorapophyllite-(Na), and hydroxyapophyllite-(K). Fluorapophyllite-(K) is the most commonly found type. The rarest, fluorapophyllite-(Na), crystallizes in the orthorhombic system, while the others form in the tetragonal system.
Apophyllite’s extremely perfect and easy cleavage makes it very fragile and dictates that gem cutters choose an orientation with the table of a faceted stone not perpendicular to the crystal’s long axis.
Fluorapophyllite rough and cut set. Crystal specimen: 7.0 x 4.2 x 2.3 cm; Portuguese-cut gem, 8.58 cts. Jalgaon, Maharashtra, India. © Rob Lavinsky, www.iRocks.com. Used with permission.
Apophyllite’s optic sign may vary. It may be uniaxial positive or negative.
Material from Poona, India shows the following properties:
No known synthetics.
Yellow apophyllite crystal with phantom on matrix, Nashik District, India. Photo courtesy of liveauctioneers.com and Marques Dos Santos, Lda.
Apophyllites may receive diamond-like carbon (DLC) and synthetic diamond film coatings. These treatments may improve the gems’ wearability and resistance to scratching.
Radiation can turn colorless material green, but heating may reverse this process.
Mumbai (Bombay), Maharashtra, India produces colorless as well as intense, apple-green colored crystals, due to the presence of iron. These iron-rich apophyllites occur in magnificent crystal groups. However, facetable material is usually rare and smaller than the colorless variety. Many other sites in Maharashtra produce apophyllites.
One of a few dozen celebrated “Disco Ball” spherical crystal clusters of apophyllites discovered in Rahuri, India in 2001. Momin Akhada well dig, Rahuri, Maharashtra State, India. © Rob Lavinsky, www.iRocks.com. Used with permission.
Other notable sources include the following locations:
Pastel pink apophyllites, 9.1 x 6.4 x 3.8 cm. San Martin, Zacatecas, Mexico. © Rob Lavinsky, www.iRocks.com. Used with permission.
Apophyllite crystal cluster on matrix, Gruevo, Rhodope Mts. Bulgaria, 4 x 2.5 x 2 cm. Photo courtesy of liveauctioneers.com and Jasper52.
Gem cutters seldom facet apophyllites. Furthermore, facetable rough greater than 10 carats in size is very rare. Stones faceted as curiosities are usually colorless. However, custom gem cutters have faceted the green Indian material.
You’re more likely to find apophyllites in mineral collections than in jewelry collections. In addition to perfect cleavage and relatively low hardness (4.5 to 5), this gem has great heat sensitivity. The heat from a jeweler’s torch may cause these gems to exfoliate. In other words, true to its etymology, apophyllite may lose flakes or “leaves” of material if heated.
Faceted apophyllite, 0.6 cts, India. Photo by Kay Günther/G-Empire The World of Gems/www.g-empire.de. Licensed under CC By-SA 4.0.
Any apophyllites used in jewelry should have protective settings. Limit them to occasional wear.
For cleaning, use a soft brush, mild detergent, and warm water. Consult our gemstone jewelry care guide for more recommendations.
Apophyllite: India (1.3, 8.6, 2.4). Photo © Joel E. Arem, PhD, FGA. Used with permission.
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