What colour is iron powder, mixture or pure？

Pure metal iron is silver-white, while iron powder is black, which is an optical problem. Due to the small surface area of reduced iron powder, there is no fixed geometric shape, while the crystal structure of iron block is geometric, so the iron block absorbs part of visible light and reflects the other part of visible light in the mirror, showing white.Iron powder does not absorb all of the light is diffuse reflection, can enter the human eye less visible light, so is black.

Based on the above reasons, we for the 98% content of contrast compares the second reduced iron powder particles for 20 mesh, 100 mesh, 200 mesh reduced iron powder, and compared the results found that: the powder particles, the greater the its color is silver, the small particles, its color is dark optical reasons can well explain the problem: coarse particles of iron powder, the density, the reflected light some more;A fine powder, with more irregular particles, absorbs more light and reflects less, so its color is dimmed.