mineral

Quartz (Agate/Chalcedony variety)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Translucent grey, tan, and white; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Translucent grey, tan, and white
Luster: Waxy to vitreous

Identified May 24, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Translucent grey, tan, and white; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Formation & geological history

Formed by the deposition of silica from groundwater in cavities of igneous or sedimentary rocks. This specimen appears to be a water-worn or weathered nodule commonly found in alluvial deposits or glacial till.

Uses & applications

Used in gemstone carvings, jewelry making, abrasive manufacturing, and as a popular specimen for rock collectors.

Geological facts

Quartz is one of the most abundant minerals in the Earth's crust. Chalcedony specifically refers to the cryptocrystalline form of silica where the crystals are too small to be seen without high magnification.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and its waxy appearance. Often found in riverbeds or gravel pits. Collectors should look for translucency when held to a light source.

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

Biotite Schist

Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]

metamorphic

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral