igneous

Druzy Quartz on Vesicular Basalt

Silicon Dioxide (SiO2) in an extrusive Mafic igneous host rock

Hardness: 7 (Quartz) / 5-6 (Basalt host); Color: Tan to dark grey host with clear to white micro-crystals; Luster: Vitreous (glassy) crystals with a dull/earthy matrix; Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture).

Hardness: 7 (Quartz) / 5-6 (Basalt host)
Color: Tan to dark grey host with clear to white micro-crystals
Luster: Vitreous (glassy) crystals with a dull/earthy matrix

Identified March 29, 2026More igneous →

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Physical properties

Formation & geological history

Formed through volcanic activity where gas bubbles trapped in cooling lava created vesicles (holes). Later, silica-rich hydrothermal fluids permeated the rock, precipitating tiny quartz crystals (druzy) inside the cavities.

Uses & applications

Primarily used as a decorative collector's specimen. Basalt is used in construction as aggregate, while druzy quartz is occasionally used in 'organic' style jewelry.

Geological facts

This specimen represents a 'lithogeode' process. The tiny crystals, known as druzy, often sparkle like sugar under direct light because of the many small crystal facets reflecting light at different angles.

Field identification & locations

Identify in the field by looking for 'bubbly' or porous volcanic rocks with shimmering crystal linings in the pores. High concentration in volcanic fields such as the Deccan Traps or the Pacific Northwest.

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