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 a natural volcanic glass that can be polished to a very high luster. Some stones of obsidian contain white crystals of the mineral cristobalite. When polished these stones produce a gemstone known as snowflake obsidian.he grossularite garnet used to make tumbled stones, beads and carvings is an opaque, massive garnet that often has an attractive green color. Much of it is found in South Africa where it has been inappropriately called Transvaal Jade (it is not jade and has no mineral relationship with jade).