Mineral / Sedimentary (often associated with volcanic hosts)

Quartz Druzy on Agate (River Cobble)

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Pale yellow to golden-brown translucent crystals on a white/grey base; Luster: Vitreous (glassy) to adamantine; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Luster: Vitreous (glassy) to adamantine

Identified March 29, 2026More mineral / sedimentary (often associated with volcanic hosts) →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed by the precipitation of mineral-rich groundwater within cavities (vugs) of host rocks. The crystals grow inward from the cavity walls. This specimen has been naturally tumbled by river or coastal erosion, giving it its rounded, teardrop shape.

Uses & applications

Used primarily for jewelry (cabochons and pendants), decorative ornaments, and as entry-level mineral specimens for collectors due to its sparkling aesthetic.

Geological facts

The term 'druzy' refers to a coating of fine crystals on a rock surface. This specific piece is a 'water-worn' specimen, meaning nature did the polishing that lapidaries usually do in a machine.

Field identification & locations

Identify in the field by looking for 'glint' or 'sparkle' in riverbeds or beaches. It feels significantly harder than glass and cannot be scratched by a steel knife. Common in volcanic regions with high silica content in the groundwater.

Other mineral / sedimentary (often associated with volcanic hosts) specimens

See all

Amygdaloidal Basalt

Amygdaloidal Basalt (Host rock) with Quartz or Calcite amygdules

igneous

Serpentinite

Serpentinite (Mg, Fe, Ni, Al, Zn)2-3(Si, Al, Fe)2O5(OH)4

metamorphic

Schist (specifically Mica Schist)

Mica Schist (primarily composed of Muscovite KAl2(AlSi3O10)(OH)2 and Biotite)

metamorphic

Banded Agate

Cryptocrystalline Silica (SiO2)

mineral

Turquoise

Hydrated copper and aluminum phosphate (CuAl6(PO4)4(OH)8·4H2O)

mineral

Orca Agate

Chalcedony (SiO2) with various inclusions

mineral