The burning of coal produces a variety of particles. Most samples contain a mixture of raw coal, coke, unfused ash and fused ash. The raw coal particles are smooth, shiny, black, angular pieces of the original product. Coal comes in three varieties; anthracite, bituminous or lignite. The coked materials are partially burned pieces of coal and are black, opaque and rough in texture. When coal is being coked, liquids are emitted. This liquid appears as a tarry sphere. The solids left behind will either appear as an unfused or fused ash. Unfused ash can appear white, yellow or brown. They are translucent to opaque due to air inclusions. Fused ash is usually seen as either clear glassy spheres or white "snowball" like spheres. Magnetite is also a byproduct of coal combustion. It appears as a black, opaque sphere and is magnetic from its high iron content. Elemental titanium is commonly used as a tracer.
Coal Flyash viewed with Stereo Microscope
This image was taken at 40x. Note the slivers of raw, unburned coal (black) and the one fused ash sphere (white).
Under the Light Microscope
This is an image of Coal Flyash taken at 100x with reflective light. Note the fused ash (the whitish to clear spheres), tarry spheres
(shiny black) and magnitite (dull black).
Sample was from a coal fired power plant.
R. Cheng A.S.R.C.
Coal flyash viewed with a Scanning Electron Microscope
Top Photo: Viewed at 1000x. Note the smooth texture to the sphrere. This sample also came from a power plant.
Bottom Photo: Same sample