Phenakite is a beryllium nesosilicate, simpler in chemistry than its better-known beryllium relative beryl. Its name comes from the Greek “phenax” (deceiver) because crystals strongly resemble quartz. Phenakite is sought for both rare gem material and its sharp rhombohedral crystals.
Properties
- Formula: Be2SiO4
- Crystal system: Trigonal
- Hardness: 7.5 – 8
- Color: Colorless, pale yellow, pink, brown, occasionally rose
- Streak: White
- Luster: Vitreous
- Cleavage: Distinct on {1120}
- Density: 2.96 g/cm³
Occurrence
Type locality: Emerald Mines, Takovaya River (Russia). Other notable: Itatiaia and Minas Gerais (Brazil), Mt. Antero (Colorado), Volyn (Ukraine), and Erongo (Namibia). Found in pegmatites and high-temperature alpine veins. Chinese material is minor.
Identification
Rhombohedral or short-prismatic crystals + glassy luster + high hardness (~8) + low density. Distinguish from quartz (lower density, hexagonal not trigonal habit when sharp) by careful crystal morphology and density.
Collector Notes
Volyn pegmatite phenakite (Ukraine) and Brazilian crystals are the gem-grade benchmarks. Often paired with beryl, topaz and tourmaline in pegmatite collections.
Found at these Localities
- Eastern Brazilian Pegmatite Province (巴西东部伟晶岩省)
- Ural Emerald Mines (乌拉尔祖母绿矿)
- Volyn (Volodarsk-Volynskii) (沃伦伟晶岩区)
- Madagascar Pegmatites (Sahatany / Antsirabe) (马达加斯加伟晶岩区)
- Ouro Preto Region (欧鲁普雷图矿区)
- Erongo Mountains (埃龙戈山)
- Swiss Alps (Alpine-Cleft Province) (瑞士阿尔卑斯高山裂隙矿物产地)
