Elbaite
Elbaite is a sodium, lithium, aluminum borosilicate hydroxide phosphate, more commonly known as a variety of tourmaline. It is one of the most sought-after and colorful members of the tourmaline group, renowned for its diverse range of colors, sometimes even within a single crystal.
Chemical Formula: Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)4
Properties:
- Color: Elbaite exhibits an extensive array of colors, including red (rubellite), pink, green (verdelite), blue (indicolite), yellow, brown, black, and colorless (achroite). Bi-colored and multi-colored crystals are common, often with concentric color zones or lengthwise color variations.
- Luster: Vitreous
- Crystal System: Trigonal
- Hardness: 7 - 7.5 on the Mohs scale
- Streak: White
- Diaphaneity: Transparent to translucent
- Cleavage: Indistinct
- Fracture: Uneven to conchoidal
- Specific Gravity: 2.90 - 3.20
- Optical Properties: Uniaxial (-)
Occurrence:
Elbaite is typically found in granite pegmatites, metamorphic rocks, and occasionally in hydrothermal veins. Notable localities include Elba Island, Italy (from which it derives its name), Brazil, Afghanistan, Nigeria, Madagascar, California (USA), and Maine (USA).
Uses:
The primary use of elbaite is as a gemstone. Its wide variety of colors, clarity, and hardness make it a popular choice for jewelry. High-quality, intensely colored elbaite specimens can command high prices. It is also collected by mineral enthusiasts.
Distinguishing Features:
Elbaite can be distinguished from other minerals by its characteristic tourmaline crystal shape (typically prismatic with rounded triangular cross-section), hardness, and often by its color zoning. Refractive index measurements can also be used to differentiate it from similar minerals.