Sedimentary and Metamorphic

Sandstone, Quartzite, and River Pebbles

Silicon Dioxide (SiO2) based Sedimentary/Metamorphic structures

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 →

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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.

Other sedimentary and metamorphic specimens

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Shale or Argillite

Shale (sedimentary) / Argillite (metamorphic)

Sedimentary or Metamorphic (low-grade)

Anthracite Coal

Anthracite (Carbon-rich Sedimentary-to-Metamorphic Rock)

metamorphic

Milky Quartz with Iron Inclusions

Quartz (Silicon Dioxide, SiO2)

mineral

Anthracite Coal

Anthracite (Carbon-based sedimentary-derived metamorphic rock)

metamorphic

Jasper Conglomerate (Puddingstone)

Siliceous Conglomerate (Quartz and Jasper clasts in a fine-grained matrix)

sedimentary

River Pebbles and Quartz

Mixed Igneous, Sedimentary, and Metamorphic Rocks (Silicon Dioxide SiO2 dominant)

mixed