mineral

Milky Quartz (Water-Worn Pebble)

Quartz (Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale. Color: Milky white to translucent. Luster: Vitreous to waxy. Crystal Structure: Hexagonal/Trigonal (though often cryptocrystalline in common pebbles). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

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

Identified March 7, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed through the cooling of silica-rich magma or from hydrothermal veins. The milky appearance is caused by microscopic inclusions of fluids or gases trapped during crystal growth. This specific specimen has been significantly weathered and rounded by water action in a river or beach environment.

Uses & applications

Industrial uses include glass making, abrasives, and electronics (due to piezoelectric properties). In jewelry, it is often used for beads or cabochons. Large specimens are popular for home decor and garden landscaping.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Historically, the 'milky' look was sometimes believed to represent frozen ice that would never melt. It is highly resistant to chemical and physical weathering, which is why quartz pebbles are so common in riverbeds.

Field identification & locations

Identify by its hardness (it will easily scratch glass) and lack of cleavage planes. To identify in the field, look for the 'greasy' luster on freshly broken surfaces. Common worldwide in gravel pits, beaches, and stream beds.

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