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Obsidian hydration dating (OHD) is a geochemical method of determining age in either absolute or relative terms of an artifact made of obsidian.. Obsidian is a volcanic glass that was used by prehistoric people as a raw material in the manufacture of stone tools such as projectile points, knives, or other cutting tools through knapping, or breaking off pieces in a controlled manner, such as ...
A modern recreation of a ceremonial Mesoamerican macuahuitl, edged with obsidian. Obsidian, used by Native Americans for knives, spearheads, and arrowheads. This natural glass chips sharper than other stones but is more brittle. Other hard stones such as flint, chert, radiolarite, chalcedony, basalt, and quartzite.
Obsidian is usually of rhyolitic composition, and it has been used for tools since prehistoric times. [34] Obsidian scalpels have been investigated for use in delicate surgery. [ 35 ] Pumice, also typically of rhyolitic composition, finds important uses as an abrasive , in concrete , [ 36 ] and as a soil amendment . [ 37 ]
Obsidian projectile point.. Obsidian is a naturally formed volcanic glass that was an important part of the material culture of Pre-Columbian Mesoamerica.Obsidian was a highly integrated part of daily and ritual life, and its widespread and varied use may be a significant contributor to Mesoamerica's lack of metallurgy.
The natural volcanic glass obsidian can achieve a nearly molecular edge (high achievable sharpness) and only requires Stone Age technology to work, [2] but is so brittle that it cannot maintain that sharpness for very long. Additionally, The entire blade is highly susceptible to being accidentally broken.
The source of obsidian for cultures inhabiting the territory of and around Greece was the island of Milos; the Starčevo–Körös–Criș culture obtained obsidian from sources in Hungary and Slovakia, while the Cardium-Impresso cultural complex acquired obsidian from the island outcrops of the central Mediterranean.
Ingot molds are tapered to prevent the formation of cracks due to uneven cooling. A crack or void formation occurs as the liquid to solid transition has an associated volume change for a constant mass of material. The formation of these ingot defects may render the cast ingot useless and may need to be re-melted, recycled, or discarded.
When the metal had cooled and hardened, the smaller ingots (the "pigs") were simply broken from the runner (the "sow"), hence the name "pig iron". [4] As pig iron is intended for remelting, the uneven size of the ingots and the inclusion of small amounts of sand are insignificant issues when compared to the ease of casting and handling.