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Granite is a hard stone and requires skill to carve by hand. Until the early 18th century, in the Western world, granite could be carved only by hand tools with generally poor results. A key breakthrough was the invention of steam-powered cutting and dressing tools by Alexander MacDonald of Aberdeen , inspired by seeing ancient Egyptian granite ...
Sling-bullets of baked clay and stone found at Ham Hill Iron Age hill fort. The simplest projectile was a stone, preferably well-rounded. Suitable ammunition is frequently from a river or a beach. The size of the projectiles can vary dramatically, from pebbles massing no more than 50 g (1.8 oz) to fist-sized stones massing 500 g (18 oz) or more.
Besides flint, other hard, non-porous rocks that can take a sharp edge can be used, such as chert, quartz, agate, jasper or chalcedony. [ 2 ] The sharp edge of the flint is used to violently strike the fire steel at an acute angle in order to cleave or shave off small particles of metal.
Electrohydraulic lithotripsy is an industrial technique for fragmenting rocks by using electrodes to create shockwaves. It was applied to bile duct stones in 1975. It can damage tissue and is mostly used in biliary tract specialty centers. Pneumatic mechanical devices have been used with endoscopes, commonly for large and hard stones. [7]
This region is also the location of the harshest conditions for hard rock mining, with air temperatures of up to 45 °C (113 °F). However, massive refrigeration plants are used to bring the temperature down to around 28 °C (82 °F). The deepest inactive hard rock mine in North America is the Empire mine in Grass Valley California. Closed in ...
Lifting a stone at Harri-jasotzaileak event in the Basque Country. Lifting stones are heavy natural stones which people are challenged to lift, proving their strength. They are common throughout Northern Europe, particularly Iceland (where they are referred to as steintökin), Ireland, Scotland, Basque Country, Faroe Islands, Wales, North West England centered around Cumbria, Switzerland ...
The stones are named for Ardblair Castle located in Blairgowrie, Perthshire in Scotland, close to where they originated. The stones were created by Charlie Blair Oliphant in 2008, based on World's Strongest Man competitions he had seen on TV as a child. Oliphant wanted to create an event that was accessible to all people, regardless of age and ...
During the Stone Age, access to flint was so important for survival that people would travel or trade long distances to obtain the stone. Grime's Graves was an important source of flint traded across Europe. Flint Ridge in Ohio was another important source of flint, and Native Americans extracted the flint from hundreds of quarries along the ridge.