Elbaite

General
Category	Tourmaline group
Formula	Na(Li1.5Al1.5)Al6(BO3)3Si6O18(OH)4
IMA symbol
Strunz classification
Dana classification
Crystal system	Trigonal
Crystal class
Space group
Unit cell

Elbaite is a sodium lithium aluminium borosilicate mineral belonging to the tourmaline group. It is one of the most colorful and well-known members of the tourmaline family, prized for its wide range of colors and its use as a gemstone. Elbaite is named after the island of Elba, Italy, where it was first discovered.

Crystal Structure and Composition

Elbaite crystallizes in the trigonal crystal system, forming prismatic crystals that are often vertically striated. The general chemical formula for elbaite is Na(Li_1.5Al_1.5)Al₆(BO₃)₃Si₆O₁₈(OH)₄. This formula highlights the presence of sodium (Na), lithium (Li), and aluminium (Al) as key components, along with boron (B), silicon (Si), and hydroxide (OH).

Physical Properties

Elbaite exhibits a hardness of 7 to 7.5 on the Mohs scale, making it suitable for use in jewelry. It has a vitreous luster and a white streak. The mineral is brittle with an uneven to conchoidal fracture and indistinct cleavage.

Optical Properties

Elbaite is uniaxial negative with strong pleochroism, meaning it can show different colors when viewed from different angles. This property, combined with its vibrant colors, makes it highly desirable for gemstone cutting.

Color Variations

Elbaite is renowned for its wide range of colors, which include:

• Rubellite: Pink to red
• Indicolite: Blue
• Verdelite: Green
• Achroite: Colorless
• Watermelon tourmaline: Pink center with a green outer layer

The color variations are due to trace elements such as iron, manganese, and chromium.

Occurrence and Localities

Elbaite is found in pegmatites, which are coarse-grained igneous rocks. Notable localities include the island of Elba in Italy, Minas Gerais in Brazil, and the state of Maine in the United States.

Uses

Elbaite is primarily used as a gemstone. Its vibrant colors and durability make it popular in rings, necklaces, and other forms of jewelry. It is also of interest to mineral collectors due to its aesthetic crystal forms.

Also see

• Tourmaline
• Pegmatite
• Gemstone
• Mohs scale of mineral hardness