How to identify Included Quartz

To correctly identify Included Quartz (SiO2 with 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, smoky, purple (amethyst), yellow (citrine), or pink (rose quartz). Inclusions add their own colors: golden (rutile), black (tourmaline, hematite), green (chlorite, actinolite), red/orange (hematite, goethite).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) on crystal faces and fresh fractures.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Crystalline, often with visible internal structures due to inclusions. Can be massive or euhedral to anhedral crystals.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Typically hexagonal prisms terminated by rhombohedra. Inclusions are internal and do not alter the external crystal habit of the quartz, though they may outline growth zones (phantoms).

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, but exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, pegmatites, igneous rocks (granites, rhyolites), metamorphic rocks (gneisses, schists), and sedimentary environments (as detrital grains). The specific type of inclusion often points to a particular formation environment (e.g., rutile in high-temperature hydrothermal veins, chlorite in lower-temperature metamorphic or hydrothermal settings).

Key Facts

Hardness

7 on the Mohs scale.

Specific Gravity

2.65 g/cm³ (for pure quartz; inclusions may slightly alter this).

Crystal System

Trigonal.

Color

Highly variable, depending on the host quartz and the type/color of inclusions.

Luster

Vitreous.

Transparency

Transparent to translucent, depending on the density and type of inclusions.

Fracture

Conchoidal.

Cleavage

None.

Composition

Silicon dioxide (SiO2) with various trapped mineral phases or fluids.

Physical characteristics

• Crystal Habit: Prismatic, often with hexagonal cross-section, terminated by rhombohedral faces. Inclusions are internal.
• Cleavage Type: Absent.
• Fracture Type: Conchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous.

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