obsidian


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obsidian

(ŏbsĭd`ēən), a volcanic glassglass,
hard substance, usually brittle and transparent, composed chiefly of silicates and an alkali fused at high temperature. Composition and Properties of Glass
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, homogeneous in texture and having a low water content, with a vitreous luster and a conchoidal fracture. The color is commonly black, but may be some shade of red or brown, and cut sections sometimes appear to be green. Like other volcanic glasses, obsidian is a lavalava
, molten rock that erupts on the earth's surface, either on land or under the ocean, by a volcano or through a fissure. It solidifies into igneous rock that is also called lava.
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 that has cooled too quickly for the contained minerals to crystallize. In chemical composition it is rich in silica and similar to granite. It is favored by primitive peoples for knives, arrowheads, spearheads, and other weapons and tools.

obsidian

A natural volcanic glass, usually black with a bright luster, that is transparent in thin slabs. See also: Stone

Obsidian

(pop culture)
Introduced in All-Star Squadron #25 (1983) in a story scripted by Roy Thomas and penciled by Jerry Ordway, the living shadow Obsidian joins the list of heroes who have turned to the dark side. Unbeknownst to him, Todd Rice was the child of Alan Scott, the original Green Lantern. Raised in Milwaukee by abusive foster parent James Rice, the teenage Todd resolved to become a hero when he discovered both his “shadow powers” and his long-lost twin, Jennie-Lynn Hayden, with whom he can communicate telepathically. Together they became Jade and Obsidian, founding members of the hero group Infinity, Inc., which comprised those heroes who continued the legacy of the Justice Society of America. Todd can merge his body with his own shadow, becoming either a three-dimensional shadow form or a two-dimensional silhouette. As Obsidian, he possesses superstrength and supervitality, can float weightlessly, and delights in showing his enemies their own dark side. Obsidian's connection with the shadow realm (Shadowlands) and his experience of seeing the darkness within the human soul caused him to go gradually insane. After many of his teammates were killed and Infinity, Inc. disbanded, he waged a one-man war against his biological and adoptive fathers. Under the mentorship of Ian Karkull, an age-old Justice Society nemesis, Obsidian has fought numerous heroes, and also partnered with the princes of darkness Dark Lord Mordru and Eclipso. His family and friends remain hopeful that Obsidian will one day reject the evil that has consumed him.

Obsidian

 

(Latin Obsidianus lapis, “Obsidius’ stone”; according to Pliny the Elder, the rock was discovered in Ethiopia by a certain Obsidius, or more accurately, Obsius), a homogeneous vitreous volcanic rock, usually dark-colored (black, reddish black), with a marked conchoidal fracture. The hardness on Mohs’ scale is 5, and the density, is 2,500–2,600 kg/m3. The rock contains about 0.5 percent water.

Obsidian polishes well. It is formed upon hardening of the viscous varieties of rhyolite lava or rhyodacite lava. Certain varieties of obsidian are used as decorative stones. In the Stone Age and Bronze Age, obsidian was used to make arrowheads, spearheads, knives, and scrapers. At present it is used mainly as an expanding filler for lightweight concretes. Obsidian is found in areas of volcanic activity—for example, in Transcaucasia and on Kamchatka in the USSR, and also in Italy and Mexico.

obsidian

[äb′sid·ē·ən]
(geology)
A jet-black volcanic glass, usually of rhyolitic composition, formed by rapid cooling of viscous lava; generally forms the upper parts of lava flows. Also known as hyalopsite; Iceland agate; mountain mahogany.

obsidian

A natural volcanic glass, usually black, with a bright luster; has relatively low water content.

obsidian

a dark volcanic glass formed by very rapid solidification of lava
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The presence of obsidian from distant sources recovered in archaeological contexts has been the primary means by which the scale and arrangement of prehistoric exchange and social networks have been reconstructed in the western Pacific, where prehistorically utilized obsidian derives from four primary source areas (Fig.
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Laskaris and his colleagues turned to a method called obsidian hydration dating (OHD) combined with a newer technique known as secondary ion mass spectrometry of surface saturation (SIMS-SS) to determine how much water had penetrated the obsidian surfaces that were exposed to the air by prehistoric humans who were chipping the rocks to make tools and weapons.
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