How to identify Gold-bearing Quartzite

To correctly identify Gold-bearing Quartzite (Quartzite (metamorphic rock) with native gold (Au)), 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

   Quartzite: typically white, gray, pink, or reddish, depending on impurities. Gold: metallic yellow to brassy yellow.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Quartzite: vitreous to greasy. Gold: metallic, bright.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Quartzite: Granoblastic, interlocking quartz grains, often sugary or glassy. Gold: visible as metallic specks, flakes, or wires within the quartzite matrix.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartzite: Anhedral, interlocking quartz grains. Gold: typically anhedral masses, flakes, wires, or dendritic forms; rarely euhedral crystals (octahedra, dodecahedra).

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartzite: None (quartz has no cleavage). Gold: None.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Metamorphic terrains, often associated with ancient cratons, greenstone belts, or orogenic belts where hydrothermal fluids have introduced gold into pre-existing quartzites or their protoliths.

Key Facts

Hardness

Quartzite: 7 on Mohs scale. Gold: 2.5-3 on Mohs scale.

Specific Gravity

Quartzite: 2.65 g/cm³. Gold: 19.3 g/cm³ (pure gold), but can vary with impurities (e.g., electrum is 12-15 g/cm³).

Crystal System

Quartzite (quartz): Trigonal. Gold: Isometric.

Color

Quartzite: white, gray, pink, red. Gold: golden yellow.

Luster

Quartzite: vitreous to greasy. Gold: metallic.

Transparency

Quartzite: translucent to opaque. Gold: opaque.

Fracture

Quartzite: conchoidal to subconchoidal. Gold: hackly.

Cleavage

Quartzite: none. Gold: none.

Composition

Quartzite: primarily SiO2. Gold: Au (native element).

Physical characteristics

• Crystal Habit: Quartzite: Granular, massive. Gold: Dendritic, arborescent, wire-like, flaky, massive, rarely octahedral or dodecahedral.
• Cleavage Type: Quartzite: None. Gold: None.
• Fracture Type: Quartzite: Conchoidal to subconchoidal. Gold: Hackly.
• Tenacity: Quartzite: Brittle. Gold: Malleable and ductile.
• Luster Type: Quartzite: Vitreous to greasy. Gold: Metallic.

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