Pezzottaite

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Pezzottaite
File:Pezzottaite.jpg
Pezzottaite crystal
General
Category	Cyclosilicate
Formula	Cs(Be₂Li)Al₂Si₆O₁₈
Strunz classification	[[Strunz classification|]]
Dana classification	[[Dana classification|]]
Crystal system	[[Crystal system|]]
Crystal class
Color	Pink to raspberry red
Physical properties
Cleavage	None
Mohs scale hardness
Luster	Vitreous
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity
Optical properties
Refractive index
Crystal habit
Other characteristics

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Pezzottaite is a rare cyclosilicate mineral that belongs to the beryl group. It was first discovered in Madagascar in 2002 and is named after the Italian mineralogist Federico Pezzotta. Pezzottaite is known for its striking pink to raspberry red color, which is due to the presence of cesium and lithium in its crystal structure.

Discovery and Naming

Pezzottaite was discovered in the Sakavalana pegmatite in the Fianarantsoa Province of Madagascar. It was initially thought to be a variety of beryl, specifically a red beryl, but further analysis revealed it to be a distinct mineral species. The mineral was named in honor of Federico Pezzotta, a curator at the Museo di Storia Naturale di Milano, who contributed significantly to the study of Madagascar's mineralogy.

Chemical Composition

The chemical formula of pezzottaite is Cs(Be₂Li)Al₂Si₆O₁₈. It is a cesium-rich member of the beryl group, with lithium substituting for some of the beryllium in the crystal structure. This unique composition is responsible for its distinct color and properties.

Crystallography

Pezzottaite crystallizes in the trigonal crystal system, which is a subset of the hexagonal system. It typically forms tabular to prismatic crystals and can exhibit a vitreous luster. The mineral is transparent to translucent and has a Mohs hardness of 8, making it suitable for use as a gemstone.

Physical Properties

Pezzottaite is known for its vibrant pink to raspberry red color, which can sometimes show chatoyancy, a cat's eye effect. It has a white streak and a conchoidal fracture. The mineral is brittle and has no cleavage. Its specific gravity is approximately 3.10.

Optical Properties

Pezzottaite is uniaxial negative with refractive indices ranging from nω = 1.608 - 1.620 and nε = 1.607 - 1.617. It exhibits weak pleochroism and does not fluoresce under ultraviolet light.

Occurrence and Localities

In addition to Madagascar, pezzottaite has been found in Afghanistan and Myanmar. It occurs in granitic pegmatites, often associated with other rare minerals such as tourmaline, spodumene, and lepidolite.

Uses

Due to its rarity and striking color, pezzottaite is primarily used as a gemstone. It is cut into various shapes and sizes for use in jewelry. However, its brittleness requires careful handling during cutting and setting.

Also see

• Beryl
• Tourmaline
• Spodumene
• Lepidolite
• Gemstone