mineral

Quartz (Milky/Gravel variety)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Milky white to translucent; Luster: Vitreous (glassy) to waxy; Crystal structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Milky white to translucent
Luster: Vitreous (glassy) to waxy

Identified March 25, 2026More mineral →

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: Milky white to translucent; Luster: Vitreous (glassy) to waxy; Crystal structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Quartz forms in all types of environments (igneous, metamorphic, sedimentary) but often crystallizes from cooling magma or hydrothermal veins. This specific rounded specimen likely originated as a vein mineral and was polished by water erosion in a river or stream bed over thousands of years.

Uses & applications

Used in glassmaking, electronics (piezoelectric properties), abrasives, and as a common component in concrete. In small gravel form, it is used for landscaping or as a basic pocket stone for collectors.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Pure quartz is clear; the 'milky' appearance of this specimen is caused by tiny fluid inclusions of gas or liquid trapped during the crystal's growth.

Field identification & locations

Identify in the field by its hardness (it should easily scratch glass) and lack of cleavage planes. Found globally in riverbeds, mountains, and beaches. For collectors, look for the 'conchoidal' fracture—the way it breaks like glass.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral