sedimentary
Chert with Quartz Veins
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Dark grey/black with white/cream veins; Luster: Waxy to dull (rock) and vitreous (veins); Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Dark grey/black with white/cream veins
- Luster
- Waxy to dull (rock) and vitreous (veins)
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Dark grey/black with white/cream veins; Luster: Waxy to dull (rock) and vitreous (veins); Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, followed by tectonic stresses that created cracks subsequently filled by hydrothermal quartz.
Uses & applications
Historically used for stone tools due to sharp edges; currently used for decorative stones, landscaping, and lapidary practice.
Geological facts
Chert is so durable that it often survives as smooth river pebbles long after the surrounding bedrock has eroded away. The white lines are 'healed' fractures where mineral-rich water deposited new quartz.
Field identification & locations
Identified by its waxy texture, extreme hardness (scratches glass), and distinctive vein patterns. Common in riverbeds, glacial tills, and coastal areas.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary