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How to identify Gold in Quartz

Au in SiO2

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To correctly identify Gold in Quartz (Au in SiO2), 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

    Gold: Bright metallic yellow, often with a slightly reddish or orange tint. Quartz: Typically colorless, white, milky, grey, or smoky.

  2. 2

    Luster

    How the surface reflects light: metallic, vitreous, dull

    Gold: Distinctive metallic luster. Quartz: Vitreous (glassy) luster.

  3. 3

    Texture

    Grain size and surface feel: coarse, fine, glassy

    Gold: Often occurs as irregular flakes, wires, dendrites, or small nuggets within the quartz. Quartz: Can be massive, granular, or crystalline.

  4. 4

    Crystal Form

    Shape of visible crystals or crystal faces

    Gold: Typically anhedral to subhedral grains, flakes, or wires; rarely forms distinct crystals (octahedra, dodecahedra, cubes). Quartz: Hexagonal prisms with pyramidal terminations, or massive/granular.

  5. 5

    Cleavage

    How it breaks: flat cleavage planes vs irregular fracture

    Gold: None (highly ductile and malleable). Quartz: None, exhibits conchoidal fracture.

  6. 6

    Geological Environment

    The rock formation and setting where it occurs

    Hydrothermal veins, often associated with fault zones, shear zones, and intrusive igneous rocks in various tectonic settings (e.g., orogenic belts, epithermal systems).

Key Facts

Hardness
Gold: 2.5-3 (Mohs); Quartz: 7 (Mohs)
Specific Gravity
Gold: 19.3 (pure); Quartz: 2.65
Crystal System
Gold: Isometric; Quartz: Trigonal
Color
Gold: Golden yellow; Quartz: Colorless to white, grey, milky, smoky
Luster
Gold: Metallic; Quartz: Vitreous
Transparency
Gold: Opaque; Quartz: Transparent to translucent
Fracture
Gold: Hackly; Quartz: Conchoidal
Cleavage
Gold: None; Quartz: None
Composition
Gold: Native element (Au); Quartz: Silicon dioxide (SiO2)

Physical characteristics

  • Crystal Habit: Gold: Dendritic, arborescent, wire-like, massive, scales, nuggets; Quartz: Prismatic, massive, granular
  • Cleavage Type: Gold: None; Quartz: None
  • Fracture Type: Gold: Hackly; Quartz: Conchoidal
  • Tenacity: Gold: Malleable, ductile, sectile; Quartz: Brittle
  • Luster Type: Gold: Metallic; Quartz: Vitreous

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