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Each paragraph should end with at least one reference, as long as it is not trivial and common knowledge. References in the middle of a paragraph are usually not valid for the sentences afterwards in the same paragraph.
The chemical composition is only given as 70-75% (probably percent by weight?) SiO2 plus MgO, Fe3O4, and water. This should be refined.
The natural weathering process of obsidian is only very shortly described (transformation to perlite) and should be expanded. It is used in archeology for estimating the age of obsidian artifacts such as spear heads and knifes.
I have a large piece of Obsidian, I think its very unusal to find this type in the area that I live (Kitchener, Ontario Canada). If anyone out there has any information on Obsidian and where it is usually found I would be quite interested to hear.
I would guess that it was eroded out of its primary deposit and carried along with a glacier. Then when the glacier receded, it dropped out. Ask your local university about moraines in your area. Woland37 18:29, 30 November 2006 (UTC)
Obsidian is rare, though sizable obsidian (even large boulders) are common at Newberry Volcanic monument in central Oregon. The reason it is rare is because it forms from high-silica lava, must cool quickly before crystals can form, and must be free of volatiles. Also keep in mind that just because a shield volcano may spew low-silica basaltic lava doesn't mean it never has (or ever will) spew high-silica rhyolitic lava, Newberry is an example. If you don't want to drill bore holes I would explore volcanic vents with recent lava flows (particularly short and jagged ones, but there are exceptions, Ring Creek lava flow is one) near glaciers. Mount Garibaldi in British Columbia is a good example having Holocene rhyodacitic lava flows and The Barrier which is a rock wall formed from the collision of lava and glacier. This MINFILE record inspired a few of us to go investigate the area last summer, but it's a good bet that any obsidian is either controlled in a park, owned by a resource company, or buried Exsuscito (talk) 22:32, 15 April 2011 (UTC)
Nice start to an article, but very biased towards the US and MesoAmerica (probably because the writers know those areas best). There's nothing on the amazing Palaeolithic, Epipalaeolithic and Neolithic obsidian tools from the Middle East, especially Iraq? I saw some fantastic long obsidian blades and blade cores in Mosul Museum in Iraq in 1989, but suspect they have long since been bombed or smashed. The Maori used obsidian in New Zealand. There are lots of other locations and cultures where obsidian occurs and has been utilised - anyone with more information able to expand? 126.96.36.199 (talk) 15:42, 11 March 2008 (UTC)
Another interesting you could post about minerals is how to cut and shape them. I have a friend who tried to cut obsidian on his own with a hammer and a chisel and ended up slicing himself something nasty. Knowing how to home shape a mineral or at least a warning not to could be useful to some. ~~Mr. Wonderful~~
Your friend is an idiot. Obsidian fractures with EXTREMELY sharp edges. Obsidian has been / is used by surgeons due to its potential for an extremely sharp edge. It is much sharper than man-made steel blades, and should not be worked except by those that understand the danger involved. If interested in working siliceous rock, do some research on flintknapping. —Preceding unsigned comment added by 188.8.131.52 (talk) 02:52, 27 February 2011 (UTC)