Rubellite in Quartz

Mineral Aggregate

Rubellite (a variety of Elbaite Tourmaline) in Quartz

Also known as: Rubellite Quartz, Pink Tourmaline in Quartz

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Description

Rubellite in Quartz is a mineral aggregate consisting of rubellite, a red to pink variety of elbaite tourmaline, embedded within a matrix of quartz. The rubellite typically occurs as prismatic crystals, often with characteristic striations parallel to the c-axis, ranging in color from pale pink to deep ruby red. These tourmaline crystals can be transparent to opaque and vary in size from microscopic needles to several centimeters in length. The quartz matrix is usually colorless and transparent to translucent, providing a stark contrast to the vibrant rubellite. The combination creates aesthetically pleasing specimens valued for their beauty and geological interest.

How to Identify

Color: The rubellite inclusions display shades of pink to red, from pale rose to deep ruby. The quartz matrix is typically colorless, white, or smoky.
Luster: Rubellite exhibits a vitreous to resinous luster. Quartz has a vitreous luster.
Texture: The texture is typically crystalline, with prismatic rubellite crystals embedded within a granular or massive quartz matrix. Rubellite crystals may show striations.
Crystal Form: Rubellite (elbaite) forms trigonal prismatic crystals, often with a characteristic triangular cross-section and vertical striations. Quartz forms hexagonal prismatic crystals, often terminated by rhombohedral faces.
Cleavage: Rubellite has indistinct cleavage parallel to the prism faces. Quartz has no true cleavage but exhibits conchoidal fracture.
Geological Environment: Primarily found in complex granitic pegmatites, which are coarse-grained igneous rocks formed from the last stages of magma crystallization. Also occurs in some hydrothermal veins associated with granitic intrusions.

Key Facts

Hardness: Rubellite (Elbaite): 7-7.5 on Mohs scale. Quartz: 7 on Mohs scale.
Specific Gravity: Rubellite (Elbaite): 3.02-3.26. Quartz: 2.65.
Crystal System: Rubellite (Elbaite): Trigonal. Quartz: Trigonal.
Color: Rubellite: Pink to red. Quartz: Colorless, white, smoky.
Luster: Vitreous to resinous (Rubellite); Vitreous (Quartz).
Transparency: Transparent to opaque (Rubellite); Transparent to translucent (Quartz).
Fracture: Conchoidal to uneven (Rubellite); Conchoidal (Quartz).
Cleavage: Indistinct (Rubellite); None (Quartz).
Composition: Rubellite: Complex borosilicate of aluminum, lithium, and manganese. Quartz: Silicon dioxide (SiO2).

Quick Check

Color: Pink to red rubellite inclusions in colorless to white or smoky quartz.
Luster: Vitreous to resinous for rubellite; vitreous for quartz.
Streak: White for both rubellite and quartz.

Physical Characteristics

Crystal Habit: Rubellite: Prismatic, often with vertical striations, sometimes acicular. Quartz: Prismatic, often terminated by rhombohedra, massive, granular.
Cleavage Type: Rubellite: Indistinct basal cleavage. Quartz: None.
Fracture Type: Rubellite: Conchoidal to uneven. Quartz: Conchoidal.
Tenacity: Brittle for both rubellite and quartz.
Luster Type: Vitreous to resinous (Rubellite); Vitreous (Quartz).

Formation

Rubellite in Quartz forms primarily in complex granitic pegmatites and, less commonly, in hydrothermal veins. The formation process involves the crystallization of silica-rich fluids (forming quartz) and boron-rich, lithium-rich, and aluminum-rich fluids (forming elbaite tourmaline, specifically the rubellite variety) under high temperatures and pressures. The tourmaline crystals grow within the quartz matrix, often as inclusions, or intergrown with the quartz during simultaneous crystallization from the same parent fluid. The characteristic red to pink color of rubellite is due to the presence of manganese (Mn) within the elbaite structure.

Usage

Primarily used as a gemstone and for ornamental purposes. Specimens with well-formed rubellite crystals encased in clear quartz are highly prized by collectors. It is also used in jewelry, often cut as cabochons or polished freeform shapes to showcase the contrasting colors and textures.

Age Distribution

Typically found in pegmatites and hydrothermal veins associated with granitic intrusions, which can range from Precambrian to Cenozoic, depending on the specific geological setting.

Where to Find

Minas Gerais, Brazil

Renowned for producing high-quality rubellite tourmaline, often found in pegmatite deposits, including specimens within quartz.

Pala, San Diego County, California, USA

Historically significant for its pegmatite mines, yielding various tourmaline varieties, including rubellite, sometimes in quartz.

Afghanistan and Pakistan

Known for producing fine tourmaline specimens from pegmatite occurrences, including rubellite, which can be found associated with quartz.

Madagascar

A significant source of various gemstones, including tourmaline, with pegmatite deposits yielding rubellite in quartz.

Mogok, Myanmar (Burma)

Famous for its gem deposits, including tourmaline, where rubellite can be found in association with quartz in pegmatitic or metamorphic environments.

Finding Tips

Target Pegmatite Localities

Focus your search on areas known for granitic pegmatites, as these are the primary geological environments for rubellite formation.

Look for Outcrops and Dumps

Examine pegmatite outcrops and mine dumps for signs of tourmaline and quartz. Weathering can expose these minerals.

Identify Associated Minerals

Rubellite in quartz often occurs with other pegmatite minerals such as feldspar, mica (lepidolite, muscovite), beryl, and spodumene. The presence of these minerals can indicate a promising locality.

Check for Color and Crystal Form

Look for the characteristic pink to red color of rubellite and the prismatic crystal habit, often embedded within clear or milky quartz.

Similar Rocks

Lepidolite in Quartz

Also known as: Lepidolite Quartz

Fuchsite in Quartz

Also known as: Green Mica in Quartz

Rhodochrosite in Quartz

Also known as: Rhodochrosite Quartz

Scientific Classification

Mineral Class: Silicates
Group: Tourmaline Group (Rubellite is a variety of Elbaite); Tectosilicates (Quartz)
Crystal System: Trigonal
Chemical Formula: Rubellite (Elbaite): Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) with Mn substitution for Li/Al. Quartz: SiO2
Composition: Rubellite: Sodium lithium aluminum borosilicate with manganese. Quartz: Silicon dioxide.

Explore Rubellite in Quartz

Identification Localities & Collecting Look-alikes

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