How to identify Included Quartz

To correctly identify Included Quartz (SiO2 with various mineral inclusions), 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

   Variable, depending on the host quartz and the inclusions. Host quartz can be colorless, white, purple, brown, or black. Inclusions can be metallic (e.g., rutile, tourmaline), green (e.g., chlorite, actinolite), red (e.g., hematite), or other colors.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) for the quartz host. Inclusions may have their own characteristic luster (e.g., metallic for rutile, silky for asbestos minerals).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically smooth, conchoidal fracture for the quartz. The texture may be interrupted or enhanced by the presence of inclusions, which can appear as needles, plates, dendrites, or amorphous masses within the quartz.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hexagonal prisms terminated by rhombohedra are common for quartz. Inclusions often follow the growth patterns of the quartz crystal (e.g., phantom growths) or appear as randomly oriented needles or fibers.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None (quartz). Inclusions may exhibit their own cleavage, but it is typically not observable within the quartz host.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, pegmatites, metamorphic rocks (schists, gneisses), sedimentary geodes, and alluvial deposits. The specific environment dictates the types of inclusions present.

Key Facts

Hardness

7 on the Mohs scale (for quartz host). Inclusions may have different hardnesses.

Specific Gravity

2.65 g/cm³ (for pure quartz). May vary slightly depending on the density and abundance of inclusions.

Crystal System

Trigonal (for quartz host).

Color

Highly variable, depending on the host quartz and the specific inclusions (e.g., colorless with golden rutile, clear with green chlorite, smoky with black tourmaline).

Luster

Vitreous.

Transparency

Transparent to translucent.

Fracture

Conchoidal.

Cleavage

None.

Composition

SiO2 (silicon dioxide) with various mineral, fluid, or gas inclusions.

Physical characteristics

• Crystal Habit: Prismatic, often terminated by rhombohedra. Inclusions can be acicular, fibrous, platy, dendritic, or amorphous within the quartz.
• Cleavage Type: None.
• Fracture Type: Conchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous.

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