How to identify Galena in Quartz

To correctly identify Galena in Quartz (PbS 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

   Galena: Silvery-gray to dark gray, often tarnishing to dull gray. Quartz: Colorless, white, or various colors (e.g., smoky, amethyst) depending on impurities.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Galena: Metallic, bright. Quartz: Vitreous (glassy).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Galena: Crystalline, often with distinct cubic or octahedral forms. Quartz: Crystalline, often massive, granular, or prismatic.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Galena: Cubic, cubo-octahedral, or octahedral crystals. Quartz: Hexagonal prisms terminated by rhombohedra.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Galena: Perfect cubic cleavage in three directions at 90 degrees. Quartz: No true cleavage, but conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, replacement deposits, and sedimentary exhalative (SEDEX) deposits, often associated with other sulfide minerals like sphalerite, pyrite, and chalcopyrite.

Key Facts

Hardness

Galena: 2.5-2.75 (Mohs); Quartz: 7 (Mohs)

Specific Gravity

Galena: 7.4-7.6; Quartz: 2.65

Crystal System

Galena: Isometric; Quartz: Trigonal

Color

Galena: Silvery-gray to dark gray; Quartz: Colorless, white, or various hues

Luster

Galena: Metallic; Quartz: Vitreous

Transparency

Galena: Opaque; Quartz: Transparent to translucent

Fracture

Galena: Subconchoidal to uneven; Quartz: Conchoidal

Cleavage

Galena: Perfect cubic on {001}; Quartz: None

Composition

Galena: Lead sulfide (PbS); Quartz: Silicon dioxide (SiO2)

Physical characteristics

• Crystal Habit: Galena: Cubic, cubo-octahedral, octahedral, massive, granular. Quartz: Prismatic, massive, granular, cryptocrystalline.
• Cleavage Type: Galena: Perfect cubic in three directions at 90 degrees. Quartz: Absent.
• Fracture Type: Galena: Subconchoidal to uneven. Quartz: Conchoidal.
• Tenacity: Galena: Brittle. Quartz: Brittle.
• Luster Type: Galena: Metallic. Quartz: Vitreous.

Explore Galena in Quartz