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171   Obs/Dacite Chips and Chunks - Medium Flat Rate Box

Medium USPS Flat Rate box packed SOLID with 20 lbs of small, thick, and odd shaped pieces of Obsidian and Dacite. Great for getting a lot of experience without the high cost of Grade A stone. Mostly small point practice material. Box price includes shipping within the domestic United States.



Price: $35.00 / Box


 
 
Product Description
Obsidian & Dacite Information

Approximately 20 lbs of small point practice material for a great price. These chips and chunks of Obsidian and Dacite are primarily small, thick, or odd shaped pieces that may contain many defects typically found in raw material. This material provides practice in the valuable skill of being able to take odd sizes and shapes and trim into usable preforms and finished items.

Do not expect high quality material in this box. Please view our higher grade material for bigger/nicer knapping stone.

Priority Mail Postage within the United States is pre-paid and included in the price of this box of Chips and Chunks. Limited boxes available.

International Customers should contact us for adjusted shipping and other limitations before purchasing.

Warning: Obsidian and dacite are some of the sharpest types of knapping stone available. Please exercise extreme caution when unpacking and handling this material because it will make you bleed very easily. Gloves and proper eye protection are required when handling this material.

General Information on Obsidian & Dacite

Obsidian

               Obsidian is mineral-like, but not a true mineral because as a glass it is not crystalline. Pure obsidian is usually dark in appearance, though the color varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to brown to black color. Very few samples are nearly colorless. In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian). It may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled. These bubbles can produce interesting effects such as a golden sheen (sheen obsidian) or an iridescent, rainbow-like sheen (rainbow obsidian).

              Obsidian can be found in locations which have experienced rhyolitic eruptions. It can be found in Argentina, Armenia, Azerbaijan, Canada, Chile, Greece, El Salvador, Guatemala, Iceland, Italy, Japan, Kenya, Mexico, New Zealand, Peru, Scotland and United States. Obsidian flows which may be hiked on are found within the calderas of Newberry Volcano and Medicine Lake Volcano in the Cascade Range of western North America, and at Inyo Craters east of the Sierra Nevada in California. Yellowstone National Park has a mountainside containing obsidian located between Mammoth Hot Springs and the Norris Geyser Basin, and deposits can be found in many other western U.S. states including Arizona, Colorado, New Mexico, Texas, Utah, Washington, Oregon and Idaho. Obsidian can also be found in the eastern U.S. state of Virginia.

             Obsidian was valued in Stone Age cultures because, like flint, it could be fractured to produce sharp blades or arrowheads. Like all glass and some other types of naturally occurring rocks, obsidian breaks with a characteristic conchoidal fracture. It was also polished to create early mirrors. Modern archaeologists have developed a relative dating system, obsidian hydration dating, to calculate the age of obsidian artifacts.

             Lithic analysis can be instrumental in understanding prehispanic groups in Mesoamerica. A careful analysis of obsidian in a culture or place can be of considerable use to reconstruct commerce, production, distribution and thereby understand economic, social and political aspects of a civilization. This is the case in Yaxchilán, a Maya city where even warfare implications have been studied linked with obsidian use and its debris. Another example is the archeological recovery at coastal Chumash sites in California indicating considerable trade with the distant site of Casa Diablo, California in the Sierra Nevada Mountains.

             Pre-Columbian Mesoamericans' use of obsidian was extensive and sophisticated; including carved and worked obsidian for tools and decorative objects. Mesoamericans also made a type of sword with obsidian blades mounted in a wooden body. Called a macuahuitl, the weapon was capable of inflicting terrible injuries, combining the sharp cutting edge of an obsidian blade with the ragged cut of a serrated weapon.

             Native American people traded obsidian throughout the Americas. Each volcano and in some cases each volcanic eruption produces a distinguishable type of obsidian, making it possible for archaeologists to trace the origins of a particular artifact. Similar tracing techniques have allowed obsidian to be identified in Greece also as coming from Melos, Nisyros or Yiali, islands in the Aegean Sea. Obsidian cores and blades were traded great distances inland from the coast.

In Chile obsidian tools from Chaitén Volcano have been found as far away as in Chan-Chan 400 km north of the volcano and also in sites 400 km south of it.

Dacite

            Dacite is an igneous, volcanic rock. The word dacite comes from Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains (now modern Romania) where the rock was first described.

            Dacite usually forms as an intrusive rock such as a dike or sill. Examples of this type of dacite outcrop are found in northwestern Montana and northeastern Bulgaria. Nevertheless, because of the moderate silica content, dacitic magma is quite viscous and therefore prone to explosive eruption. A notorious example of this is Mount St. Helens in which dacite domes formed from previous eruptions.

           Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. Oceanic crust is hydrothermally altered causing addition of quartz and sodium. As the young, hot oceanic plate is subducted under continental crust, the subducted slab partially melts and interacts with the upper mantle through convection and dehydration reactions. Once at the cold surface, the sodium rich magma crystallizes plagioclase, quartz and hornblende. Accessory elements like pyroxenes provide insight to the history of the magma.

The formation of dacite provides a great deal of information about the connection between oceanic crust and continental crust. It provides a model for the generation of felsic, buoyant, perennial rock from a mafic, dense, short-lived one.

From Wikipedia, the free encyclopedia



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GoKnapping, LLC
PO Box 803
Petal, MS 39465
Email: Info@GoKnapping.com 

 
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