sedimentary
Chert (Yellow Jasper/Flint)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Ocher, tan, brown; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Ocher, tan, brown
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 Mohs; Color: Ocher, tan, brown; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed in marine or freshwater environments by the accumulation of siliceous remains of organisms or chemical precipitation. These specimens are often millions of years old and are frequently reshaped by river or glacial action.
Uses & applications
Historically used for stone tools and arrowheads due to sharp edges when fractured. Modernly used in lapidary work, jewelry (tumbled stones), and as decorative filler.
Geological facts
Chert is so hard it can strike sparks from steel. Varieties include Jasper (red/yellow/brown), Flint (dark grey/black), and Agate (banded). This specimen appears to be water-worn and possibly wet, enhancing its color.
Field identification & locations
Identify by its waxy luster, smooth surface, and conchoidal fracture (curving breaks like glass). It is commonly found in riverbeds, gravel pits, and sedimentary rock outcrops globally.
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