Home > Lithic reduction

In prehistoric times, cryptocrystalline stones such as chert, flint, obsidianObsidian is a type of naturally occurring glass, produced from volcanoes when the right kind of lava cools rapidly, e. by flowing into a body of water. It consists mainly of SiO (silicon dioxide), 70% or more. Obsidian is mineral-like, but not a true mine, and chalcedonyChalcedony is one of the cryptocrystalline varieties of the mineral quartz, having a waxy luster. It may be semitransparent or translucent and is usually white to gray, grayish-blue or some shade of brown, sometimes nearly black. Other shades have been gi, as well as some finegrained rhyoliteRhyolite is an igneous, volcanic ( extrusive) rock, of felsic composition, with aphanitic to porphyritic texture. Mineral assembly is usually quartz, alkali feldspar and plagioclase (in a ratio > 1:2). Biotite and pyroxene are common accessory minerals.s, felsiteFelsite is a very fine to cryptocrystalline igneous rock that may or may not contain larger crystals, called phenocrysts, that are typical of many porphyritic igneous rocks. The mass of the rock consists of a fine-grained matrix of felsic materials, partis, quartziteQuartzite is a hard, metamorphic rock which was originally sandstone. Through heating and pressure usually related to tectonic compression within orogenic belts, the original quartz sand grains and quartz silica cement were fused into one. Pure quartzites and a few other tool stones, were often used as a source material for stone tools. These materials are easily broken and fracture in a Hertzian coneA Hertzian cone is cone of force that propagates through a brittle, amorphous or cryptocrystalline solid material from a point of impact, eventually removing a full or partial cone; this result is familiar to anyone who has seen what happens to a plate-gl when struck with sufficient force. In this kind of fracture, a cone of force propagates through the material from the point of impact, eventually removing a full or partial cone; this result is familiar to anyone who has seen what happens to a plate-glass window when struck by a small object, such as an airgun projectileA projectile is any object sent through the air by the application of some force. In a general sense, even a football or baseball may be considered a projectile, but in practical action most projectiles are designed as weapons. Motive force Arrows, darts,. The partial Hertzian cones produced during lithic reduction are called flakes, and exhibit features characteristic of this sort of breakage, including striking platforms, bulbs of force, and occasionally eraillures, which are small secondary flakes detached from the flake's bulb of force. Flakes are often quite sharp, with distal edges only a few millimeters thick, and can be used directly or modified into other types of tools such as spokeshaves and scrapers. Occasionally, obsidian flakes are used for delicate surgery instead of steel blades, due to their preternatural sharpness.