Volcano Ash

Volcano ash or volcanic dust (in some places called "silica" although this name is not exactly accurate) consists of tiny glass or congealed lava fragments which have been blown into the atmosphere during the eruptions of volcanoes. It is a type of extrusive rock, that has been forced out or extruded onto the earth's surface. Under a microscope or a hand lens, ash is seen to contain small curved pieces of glass which are the broken walls of bubbles of the lava rock which burst from the volcano. Ash can easily be distinguished from other rocks, principally sand, by its white to bluish-gray color. lts glassy surfaces sparkle in the sun, and its particles do not dissolve in acid as do particles of limestone and chalk. It is used for many purposes; in toothpastes and powders, as abrasives cleaning compounds, glazes for pottery, in filters, and in the manufacture of cement and road asphalt.