mineral

Quartz (Agate/Chalcedony variety)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Translucent tan to smoky brownish-grey; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Translucent tan to smoky brownish-grey
Luster: Vitreous to waxy

Identified June 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of igneous rocks or sedimentary formations. Many specimens found in riverbeds originate from volcanic basalts that have weathered away.

Uses & applications

Used in gemstone carving, jewelry (cabochons), as an abrasive in industrial applications, and widely collected as pocket stones or river rocks.

Geological facts

Quartz is one of the most abundant minerals in Earth's crust. If it has banding, it is technically an agate; if it is translucent and waxy without banding, it is called chalcedony.

Field identification & locations

Identify by its hardness (will scratch glass) and smooth, waxy surface when water-worn. Common in river beds and gravel pits worldwide. Collectors should look for translucency and color depth.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

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