Le long de main Street à Alachua, Floride. Alachua Woman's Club, construit en 1912, et construit de la roche de chert ou sédimentaire qui a été extraite localement.
4500 x 3321 px | 38,1 x 28,1 cm | 15 x 11,1 inches | 300dpi
Date de la prise de vue:
23 juin 2021
Lieu:
North Central Florida, USA
Informations supplémentaires:
Chert is a sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). It occurs as nodules, concretionary masses, and as layered deposits. Chert breaks with a conchoidal fracture, often producing very sharp edges. Early people took advantage of how chert breaks and used it to fashion cutting tools and weapons. "Chert" and "flint" are names used for the same material. Both are varieties of chalcedony. 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 8000 BC, the people of what are now England and France dug shafts up to 300 feet deep into layers of soft chalk to mine chert nodules. These are some of the oldest underground mining operations ever discovered.
