Euclase is a beryllium-aluminum nesosilicate prized for its rare gem-grade aquamarine-blue crystals. The name (Greek “eu-klasis”, easy to break) reflects its perfect prismatic cleavage that makes faceted euclase a connoisseur’s gem rarely seen outside specialist collections.
Properties
- Formula: BeAlSiO4(OH)
- Crystal system: Monoclinic
- Hardness: 7.5
- Color: Sky-blue (most prized), aquamarine, colorless, pale green, yellow
- Streak: White
- Luster: Vitreous
- Cleavage: Perfect on {010}
- Density: 3.0 – 3.1 g/cm³
Occurrence
Premier sources: Ouro Preto and Capão (Minas Gerais, Brazil) for sky-blue gem crystals; Last Hope Mine (Zimbabwe) for the deepest blue color; Russia and Pakistan for additional material.
Identification
Sky-blue color + perfect lateral cleavage + monoclinic prismatic crystals + association with quartz/beryl in pegmatites or alpine clefts. Distinguish from aquamarine (beryl, hexagonal, no perfect cleavage).
Collector Notes
Brazilian sky-blue euclase from Ouro Preto is among the most coveted of all gem rarities. The cleavage makes faceting tricky — euclase gems are connoisseur targets.
Found at these Localities
- Eastern Brazilian Pegmatite Province (巴西东部伟晶岩省)
- Madagascar Pegmatites (Sahatany / Antsirabe) (马达加斯加伟晶岩区)
- Ouro Preto Region (欧鲁普雷图矿区)
- Swiss Alps (Alpine-Cleft Province) (瑞士阿尔卑斯高山裂隙矿物产地)
