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 More igneous →
Explore Druzy Quartz on Vesicular Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
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).
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.
