How to identify Stibnite with Quartz

To correctly identify Stibnite with Quartz (Stibnite (Sb2S3) with 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

   Stibnite: Lead-gray to steel-gray, often tarnishing to iridescent blue or black. Quartz: Colorless, white, gray, or smoky.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Stibnite: Metallic to submetallic. Quartz: Vitreous (glassy).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Stibnite: Typically forms elongated, acicular, or bladed crystals, often in radiating or parallel aggregates. Can be massive. Quartz: Crystalline, granular, or massive.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Stibnite: Orthorhombic, typically as prismatic, acicular, or bladed crystals, often striated parallel to the c-axis. Quartz: Hexagonal, typically as prismatic crystals with pyramidal terminations, or massive.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Stibnite: Perfect cleavage parallel to {010}, leading to easy splitting into thin, flexible blades. Quartz: No true cleavage, conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, hot spring deposits, and replacement deposits, often associated with volcanic or metamorphic terrains. Found in low-temperature to moderate-temperature environments.

Key Facts

Hardness

Stibnite: 2-2.5 (Mohs); Quartz: 7 (Mohs)

Specific Gravity

Stibnite: 4.52-4.62; Quartz: 2.65

Crystal System

Stibnite: Orthorhombic; Quartz: Trigonal (often appears hexagonal)

Color

Stibnite: Lead-gray to steel-gray, tarnishes iridescent; Quartz: Colorless, white, gray, smoky

Luster

Stibnite: Metallic to submetallic; Quartz: Vitreous

Transparency

Stibnite: Opaque; Quartz: Transparent to translucent

Fracture

Stibnite: Subconchoidal to uneven; Quartz: Conchoidal

Cleavage

Stibnite: Perfect on {010}; Quartz: None

Composition

Stibnite: Antimony sulfide (Sb2S3); Quartz: Silicon dioxide (SiO2)

Physical characteristics

• Crystal Habit: Stibnite: Acicular, bladed, prismatic, often in radiating or parallel aggregates, massive. Quartz: Prismatic, massive, granular.
• Cleavage Type: Stibnite: Perfect {010}; Quartz: None
• Fracture Type: Stibnite: Subconchoidal to uneven; Quartz: Conchoidal
• Tenacity: Stibnite: Sectile, brittle, flexible in thin laminae; Quartz: Brittle
• Luster Type: Stibnite: Metallic to submetallic; Quartz: Vitreous

Explore Stibnite with Quartz