Sedimentary and Metamorphic

Sandstone, Quartzite, and River Pebbles

Silicon Dioxide (SiO2) based Sedimentary/Metamorphic structures

AI-generated identification · may be incorrect

Hardness: 6-7 Mohs; Colors: Tan, grey, reddish-brown; Luster: Dull/Earthy to slightly Waxy; Structure: Clastic or Granoblastic; Cleavage: None/Conchoidal fracture.

Hardness: 6-7 Mohs
Luster: Dull/Earthy to slightly Waxy

Identified March 19, 2026More sedimentary and metamorphic →

Explore Sandstone, Quartzite, and River Pebbles in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6-7 Mohs; Colors: Tan, grey, reddish-brown; Luster: Dull/Earthy to slightly Waxy; Structure: Clastic or Granoblastic; Cleavage: None/Conchoidal fracture.

Formation & geological history

Formed through the accumulation of sand grains (sandstone) or the heat/pressure metamorphization of those sands (quartzite). The rounded shapes indicate erosion in high-energy water environments like rivers or beaches.

Uses & applications

Construction aggregate, decorative landscaping, glass manufacturing (if high purity silica), and historical use as building stone or sharpening tools.

Geological facts

The stack displays stones in various stages of the rock cycle: the base is a block of rough sandstone, the middle red stone is likely arkose or oxidized sandstone, and the top rounded grey stones are river-worn clasts.

Field identification & locations

Identify in the field by their gritty texture (sandstones) or smooth, water-worn surfaces (river stones). Commonly found in dry riverbeds, alpine glacial deposits, and coastal regions worldwide.