Top Customer Reviews. Failure of an off-side windshield wiper blade resulted in an arc of light scratches on the glass of my concours-winning collector car. Ranging from almost-undetectable to 'can just feel them under my fingernail' the scratches caught the light and weren't going to pass muster at my next car show.
An obsidian rock is an extrusive igneous rock that forms when a volcano erupts and has no time to crystallize, so it has a glassy texture. Obsidian rocks are generally black i â¦ n color.o rock is completely impermeable, but some porous rocks like shale and pumice are mostly impermeable, because â¦ the pores are not interconnected, thus not allowing fluids or gases to pass through them. This is why shale makes a good cap-rock, and pumice floats instead of sinking. 2 people found this useful.
Black Obsidian has been used since Paleolithic times for making tools and weapons because it holds a sharp edge. Black Obsidian Geological Description: Obsidian is a glassy, silica rich rock formed from lava with a hardness of 5 to 5.5. It is an amorphous stone meaning that its structure contains no regular geometric pattern. Obsidian is found in South America, Japan, Mexico, Afghanistan, and parts of the United States.