Rare phenakite is a very hard gem material suitable for jewelry. Usually colorless, cut stones have little fire but can be very bright.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Hexagonal. Crystals rhombohedral, prismatic, acicular; also granular, and in fibrous spherulites.|
|Colors||Colorless; also yellow. pink, brown, pinkish red, all due to surface stains; some crystals are colored by impurities.|
|Cleavage||Indistinct, 1 direction.|
|Luminescence||Pale greenish or blue in UV light, occasionally pale rose. Sometimes fluoresces blue in X-rays.|
|Pleochroism||Observed in strongly colored crystals; for example, in a greenish-blue stone: violet-red/intense blue.|
|Optics||o = 1.654; e = 1.670. Uniaxial (+).|
|Etymology||From the Greek phenakos for “deceiver,” because this gem was mistaken for quartz.|
|Occurrence||In granite pegmatites, often in good crystals. Also, schist-hosted deposits of emerald and alexandrite.|
|Inclusions||Crystals of aikinite; also mica (Brazil). Fine, needle-like tubes can cause cat's eye stones in rare cases.|
Phenakites can show pale yellow, pink, and brown colors, as well as no color. (You’ll seldom see very rare red gems cut from Russian material). With little dispersion, these gems hadn’t generated much excitement beyond collectors of unusual minerals. However, the surge of New Age interest in crystals in the 1990s caught up with this stone. With or without mystical auras, exceptional hardness (7.5 – 8) and indistinct cleavage make this a good, if unusual, jewelry stone.
Labs have synthesized this mineral, starting with a seed of willemite, no less. However, you’re more likely to encounter quartz gems either erroneously or deliberately presented as phenakites. As rough, this mineral can live up to its etymology. In at least one case, near-colorless phenakite rough was submitted for gemological analysis as suspected diamond. Despite outward similarities, including trigon-like features, these gems have very different optical and physical properties. For example, phenakite has birefringence and a lower specific gravity than diamond.
Radiation treatments can turn colorless phenakites yellow-brown.
Gem-quality sources include:
- United States: Pala County, California; Colorado (Pike’s Peak area); Lords Hill, Maine; New Hampshire; Virginia (crystals up to 2 inches across).
- Habachtal, Austria: small gemmy colorless or yellowish crystals.
- San Miguel de Paracicaba, Brazil: large colorless crystals, often clean and cuttable.
- Russia: reddish color gems.
- Czech Republic; France; Madagascar; Myanmar; Klein Spitzkopje, Namibia; Nigeria; Kragero, Norway; Slovakia; Sri Lanka; Switzerland; Usugara district, Tanzania.
Faceted gemstones normally range between 1 and 5 carats in size.
Crystals up to 5 x 10 x 18 cm have been found, although usually heavily flawed. The largest known rough was a pebble found in Sri Lanka. Weighing in at 1,470 carats, it cut a 569 carat clean gem and several smaller stones. The large stone has many needle-like inclusions.
- Smithsonian Institution (Washington, DC): 22.2 (colorless, Russia); 21.9 (colorless, Brazil).
- National Museums of Canada (Ottawa, Ontario): 23.41 (colorless, Brazil).
- Private Collection: 21.21, 19.17 (colorless, Russia).
These gems require no special care. See our Gemstone Jewelry Cleaning Guide for care recommendations.
Here’s a video showing a full view of that finished 35.95-ct phenakite. Video © Dan Stair Custom Gemstones. Used with permission.