How to identify Galena-Sphalerite-Quartz Ore

To correctly identify Galena-Sphalerite-Quartz Ore (Galena (PbS), Sphalerite ((Zn,Fe)S), Quartz (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: Lead-gray to silvery-gray. Sphalerite: Highly variable, yellow, brown, black, reddish-brown. Quartz: Colorless, white, gray, or various other colors due to impurities.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Galena: Metallic. Sphalerite: Resinous to adamantine. Quartz: Vitreous (glassy).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Galena: Often granular, massive, or well-formed cubic/octahedral crystals. Sphalerite: Massive, granular, botryoidal, or crystalline. Quartz: Crystalline, massive, granular.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Galena: Cubic, octahedral, or cubo-octahedral crystals; also massive. Sphalerite: Tetrahedral crystals, often massive, granular, or botryoidal. Quartz: Hexagonal prisms with pyramidal terminations; massive, granular.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Galena: Perfect cubic cleavage in three directions at 90 degrees. Sphalerite: Perfect dodecahedral cleavage in six directions. Quartz: No cleavage, conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, Mississippi Valley-type (MVT) deposits, volcanogenic massive sulfide (VMS) deposits, skarns, and replacement deposits in carbonate rocks. Often found in association with other sulfides like pyrite, chalcopyrite, and carbonates like calcite or dolomite.

Key Facts

Hardness

Galena: 2.5-2.75 (Mohs); Sphalerite: 3.5-4 (Mohs); Quartz: 7 (Mohs).

Specific Gravity

Galena: 7.4-7.6; Sphalerite: 3.9-4.1 (increases with Fe content); Quartz: 2.65.

Crystal System

Galena: Isometric; Sphalerite: Isometric; Quartz: Trigonal.

Color

Galena: Lead-gray; Sphalerite: Yellow, brown, black, red; Quartz: Colorless, white, gray, purple, pink, etc.

Luster

Galena: Metallic; Sphalerite: Resinous to adamantine; Quartz: Vitreous.

Transparency

Galena: Opaque; Sphalerite: Translucent to transparent (thin splinters); Quartz: Transparent to translucent.

Fracture

Galena: Subconchoidal to uneven; Sphalerite: Conchoidal to uneven; Quartz: Conchoidal.

Cleavage

Galena: Perfect cubic {001}; Sphalerite: Perfect dodecahedral {011}; Quartz: None.

Composition

Galena: Lead sulfide (PbS); Sphalerite: Zinc iron sulfide ((Zn,Fe)S); Quartz: Silicon dioxide (SiO2).

Physical characteristics

• Crystal Habit: Galena: Cubes, octahedra, cubo-octahedra, massive, granular. Sphalerite: Tetrahedra, dodecahedra, massive, granular, botryoidal. Quartz: Prismatic, massive, granular, cryptocrystalline.
• Cleavage Type: Galena: Perfect cubic; Sphalerite: Perfect dodecahedral; Quartz: None.
• Fracture Type: Galena: Subconchoidal to uneven; Sphalerite: Conchoidal to uneven; Quartz: Conchoidal.
• Tenacity: Galena: Brittle; Sphalerite: Brittle; Quartz: Brittle.
• Luster Type: Galena: Metallic; Sphalerite: Resinous to adamantine; Quartz: Vitreous.

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