mineral

Quartz (Smoky Quartz variant)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Grayish-brown to translucent; Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grayish-brown to translucent
Luster: Vitreous (glassy)

Identified May 14, 2026More mineral →

Explore Quartz (Smoky Quartz variant) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Grayish-brown to translucent; Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the crystallization of silica-rich hydrothermal solutions or as a late-stage mineral in igneous pegmatites. The smoky color is often caused by natural irradiation of aluminum impurities within the crystal lattice.

Uses & applications

Used in electronics (as piezoelectric crystal), glassmaking, jewelry (as a gemstone), and as a popular specimen for mineral collectors.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Smoky quartz is the national gem of Scotland, where it is often referred to as 'Cairngorm' after the mountains where it is found.

Field identification & locations

Identify in the field by its hardness (will scratch glass), lack of cleavage, and translucent appearance. Often found as water-worn pebbles in riverbeds or in quartz veins within granite outcrops.