Chert Arrowhead: A chert flint arrowhead bound to a wooden arrow shaft with sinew. Chert cabochons: Occasionally, specimens of chert with attractive colors or interesting patterns are cut as gemstones.
These chert cabochons are examples. Chert has very few uses today; however, it was a very important tool-making material in the past. Chert has two properties that made it especially useful: 1 it breaks with a conchoidal fracture to form very sharp edges, and, 2 it is very hard 7 on the Mohs Scale.
The edges of broken chert are sharp and tend to retain their sharpness because chert is a very hard and very durable rock. Thousands of years ago people discovered these properties of chert and learned how to intentionally break it to produce cutting tools such as knife blades, arrowheads, scrapers, and ax heads. Tons of chert fragments have been found at locations where these objects were produced in what was one of the earliest manufacturing activities of people.
Chert is not found everywhere. It was a precious commodity that early people traded and transported long distances. As early as BC, the people of what are now England and France dug shafts up to feet deep into layers of soft chalk to mine chert nodules. These are some of the oldest underground mining operations ever discovered.
Flintlock: A close-up of the lock of a flintlock rifle, a weapon of the 18th century used in the Revolutionary War. Note the piece of chert flint in the hammer.
Chert is a very hard material that produces a spark when it is struck against steel. The heat from this spark can be used to start fires. A "flintlock" is an early firearm in which a charge of gunpowder is ignited by a flint hammer striking a metal plate see photo. A variety of metamorphosed chert known as " novaculite " has a porous, even texture that makes it useful as a sharpening stone. The Arkansas Novaculite Formation has become world famous as a source of high-quality sharpening stones and novaculite abrasive products.
How Does It Form? What Is It Used For? Article by: Hobart M. Find Other Topics on Geology. Maps Volcanoes World Maps. Diatoms are microscopic, single-celled algae that live in marine or fresh water. They produce hard parts made of silicon dioxide. NASA Image. Hardness Picks. Rock, Mineral and Fossil Collections.
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All the attributes of chert strengthen it against erosional wear. You'll see it often as an ingredient of stream gravel, conglomerates and, if you're lucky, as the star character in jasper-pebble beaches, naturally tumbled to its best appearance.
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Andrew Alden. Geology Expert. Andrew Alden is a geologist based in Oakland, California. He works as a research guide for the U. Geological Survey. Updated January 08, Featured Video. Cite this Article Format. Alden, Andrew. Gallery of Chert Rocks and Gemstones. Get to Know 24 Types of Sedimentary Rock.
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