How have the rest of you seen obsidian used? I know it as a "black stone", or as my dictionary says, "volcanic glass that is generally black". Here is how I saw it used in a book I am reading: The context was that for 50 years this man had not reflected much about his early past, thinking he could always retrieve it with ease. "How very disconcerting, the obsidian face that it now presented to him".
My dictionary only discusses the "black stone" definition. Comments???
A fellow logophile tells me: "Obsidian faced is probably less good than "granite" faced. It would suggest lack of smooth contour and angularity." I am not sure what he means by "less good".
I have found that "obsidian's" roots are interesting. Two sources have said that it is from the Latin word, "obsidianus", but was misread as being from "obsianus (lapus)". Arnie, what does "obsidianus" mean? There also was a reference to it coming from "Obsius", a Roman who supposedly discovered it, or a similar mineral.
Obsianus was a kind of black glass named after its discoverer, one Obsius. The older editions of Pliny read Obsidius and Obsidianus; hence the name obsidian applied to the stone.
I remember seeing obsidian tools when, as a boy, I visited ancient Aztec sites in Mexico, and I'd feel pretty sure obsidian was discovered in prehistoric times. It is much like a very dark glass, and with a bit of chipping early man could give it an extremely sharp edge, suitable for a knife or arrowhead. You can see some examples from early Mexico here, though the site dates them very poorly.
It may be though that Pliny credited Obsian with the discovery of the material itself, or with the discovery of a major source. While looking this up, I learned that apparantly the name Obsian became obsidian due to a typographical error inserting the '-di-'.
Quoting from Geology by Stanley Chernicoff, p. 69 (Worth Publishers, 1995):
"Volcanic Glass When lava from a volcano erupts into the air or flows into a body of water, much of it cools so quickly that its ions don't have enough time to form any crystals at all. The ions are essentially frozen in place randomly, bonded to any available ions nearby. The texture of the resulting rock is described as glassy. There are two common types of volcanic glass. Pumice (from the Latin spuma, or "foam") forms when bubbling, highly gaseous, silica-rich magma cools instantaneously. Some pumice has so many tiny cavities that it can float. Large rafts of pumice blown from coastal and island volcanoes have been known to float out to sea for hundreds of kilometers before they finally became waterlogged and sank.
"The second type of volcanic glass is obsidian. Obsidian forms when very silica-rich magmas, containing less gas than those that produce pumice, cool instantaneously. Because of the disordered arrangement of its ions, obsidian lacks an organized crystal structure and therefore does not exhibit the systematic internal plates of weakness that characterize most crystals. For this reason, it breaks by fracture rather than by cleavage. Early humans worked obsidian to fashion projectile points and sharp-edged cutting tools. (To demonstrate the quality of such ancient tools, in 1986, David Pokotylo, the curator of archaeology at the University of British Columbia's Museum of Anthropology, underwent hand surgery with an obsidian microblade scapel prepared in the style of ancient obsidian-tool making. To the surprise of the surgical team, Dr. Pokotylo's incisions healed more rapidly and more cleanly than those made with conventional steel blades.)"
