Obsidian

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Obsidian
Lipari-Obsidienne (5).jpg
General
Category Volcanic glass
Formula
(repeating unit)
70–75% SiO2,
plus MgO, Fe3O4
Identification
Color Deep black
Fractur Conchoidal
Mohs scale hairdness 5–6[1]
Luster Vitreous
Specific gravity ~2.4[2]
Optical properties Translucent
References [3]

Obsidian is a naiturally occurrin volcanic glass furmed as an extrusive igneous rock.

It is produced when felsic lava extrudit frae a volcano cuils rapidly wi minimum crystal growth. Obsidian is commonly foond within the margins o rhyolitic lava flows kent as obsidian flows, whaur the chemical composeetion (heich silica content) induces a heich viscosity an polymerization degree o the lava. The inhibition o atomic diffusion through this heichly viscous an polymerized lava explains the lack o crystal growth. Obsidian is haird an brittle; it tharefore fracturs wi very sharp edges, which haed been uised in the past in cuttin an piercin tuils, an haes been uised experimentally as surgical scalpel blades.[4]

References[eedit | eedit soorce]

  1. Peter Roger Stuart Moorey (1999). Ancient mesopotamian materials and industries: the archaeological evidence. Eisenbrauns. pp. 108–. ISBN 978-1-57506-042-2. 
  2. Geological Survey (U.S.) (1981). Geological Survey (U.S.). The Survey. pp. 185–. 
  3. Obsidian. Mindat.org
  4. Brian Cotterell; Johan Kamminga (1992). Mechanics of pre-industrial technology: an introduction to the mechanics of ancient and traditional material culture. Cambridge University Press. pp. 127–. ISBN 978-0-521-42871-2. Retrieved 9 September 2011.