How to identify Rubellite in Quartz

To correctly identify Rubellite in Quartz (Rubellite (a variety of Elbaite Tourmaline) in Quartz), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   The rubellite inclusions display shades of pink to red, from pale rose to deep ruby. The quartz matrix is typically colorless, white, or smoky.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Rubellite exhibits a vitreous to resinous luster. Quartz has a vitreous luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   The texture is typically crystalline, with prismatic rubellite crystals embedded within a granular or massive quartz matrix. Rubellite crystals may show striations.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   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.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Rubellite has indistinct cleavage parallel to the prism faces. Quartz has no true cleavage but exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   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).

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).

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