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.
Obsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure.It is an amorphous material known as a  mineraloid ..The result is a volcanic glass with a smooth uniform texture that breaks with a conchoidal fracture (see photo on right). Obsidian is usually an extrusive rock-one that solidifies above Earth's surface.However, it can form in a variety of cooling environments: Black is the most common color of obsidian.he first use of obsidian by people probably occurred when a sharp piece of obsidian was used as a cutting tool. People then discovered how to skillfully break the obsidian to produce cutting tools in a variety of shapes.