sedimentary
Chert (Yellow Jasper/Quartzite Pebble)
Microcrystalline Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: tan to honey-yellow, Luster: waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to honey-yellow, Luster: waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolarians) or chemical precipitation from groundwater. This specific specimen appears to be water-worn, smoothed by alluvial or marine transport over millions of years.
Uses & applications
Used primarily in landscaping, road construction (as gravel), and historically as a material for stone tools (lithics) due to its sharp edges when broken.
Geological facts
Because of its high hardness and lack of cleavage, this material was used by prehistoric humans to create arrowheads and scrapers. It can produce sparks when struck against steel.
Field identification & locations
Identify in the field by its hardness (it should scratch glass), waxy feel, and smoothed, rounded outer surface. It is commonly found in riverbeds, along beaches, and within sedimentary conglomerate layers.
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