sedimentary
Chert (Arrowhead Preform)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 7 (Mohs scale), Color: White to light grey with dark inclusions, Luster: Waxy to dull (patinated), Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: White to light grey with dark inclusions, Luster: Waxy to dull (patinated), Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture)
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation in sedimentary environments. This specimen shows a weathered surface or "patina" over a lithic fragment worked by humans.
Uses & applications
Historically used for making stone tools (lithics) such as arrowheads and scrapers due to its sharp edges; industrially used as an abrasive or filter medium.
Geological facts
Chert is one of the most common materials found at archaeological sites worldwide. It can vary significantly in color based on impurities like iron oxide or organic matter.
Field identification & locations
Identify by its 'conchoidal' (glass-like) fracture patterns and ability to scratch glass. This specific piece appears to be a stone tool 'preform', a partially worked piece intended to be finished into a point.
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