sedimentary

Quartz Pebble

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Cream, tan, or white; Luster: Vitreous to waxy (smooth from tumbling); Crystal Structure: Hexagonal (cryptocrystalline in this form); Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Cream, tan, or white
Luster: Vitreous to waxy (smooth from tumbling)

Identified March 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the erosion of larger igneous or metamorphic rocks (like granite or quartzite). The rounded shape is the result of mechanical weathering, specifically saltation in a stream, river, or beach environment, which smooths the edges over time.

Uses & applications

Used in construction as aggregate, in landscaping, as a source for industrial silica, and as a common find for beginner rock collectors.

Geological facts

Quartz is one of the most abundant minerals in Earth's crust and is highly resistant to chemical weathering, which is why it often remains as pebbles while other minerals dissolve.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by steel) and lack of visible grain or cleavage. These are commonly found in gravel pits, riverbeds, and along shorelines worldwide.