Why does vermiculite have gold or silver on its surface?
The reasons for the surface of vermiculite are gold or silver: the surface color of vermiculite is false color, and the selective absorption of minerals by visible light is the main reason for the color of objects.
Vermiculite is a natural, inorganic, non-toxic mineral that expands at high temperatures. It is a relatively rare mineral, belonging to silicates. The crystal structure is monoclinic, and it looks like mica from its appearance. Vermiculite is produced by the hydration of certain granite. It is commonly produced with asbestos. Because vermiculite has the ability of ion exchange, it has a great effect on the nutrition of the soil. In 2000, the total output of vermiculite in the world exceeded 500 thousand tons. The major producers are China, South Africa, Australia, Zimbabwe and the United states.
Vermiculite can be according to the stages can be divided into vermiculite and expanded vermiculite, according to color classification can be divided into golden vermiculite, vermiculite, vermiculite milky white silver white.The selective absorption of minerals by visible light is the main reason for the color of objects. Different colors of light waves are typically represented in different wavelengths, in nanometers, 1nm=109m. The visible light wavelength between 390 - 760nm, the wavelength from long to short in order to show the red orange yellow green blue purple color. Their blend color is white.Minerals are varied in color. One of the reasons for color rendering is that the white light passes through minerals during the process of internal electron transition, resulting in selective absorption of different light colors. The other is caused by physical optical processes. The main cause of the internal electron transition in minerals is the existence of pigment ions, such as Fe3+, which makes hematite red and V3+ makes vanadium garnet green. It is the lattice defects that form "color centers", such as the purple of fluorite. In mineralogy, colors are generally divided into 3 categories: self color is the intrinsic color of minerals; color is the color caused by mixing; false colors are due to some physical optical process. Such as bornite fresh face is red copper oxide film due to surface oxidation, caused by the interference of light and blue purple tarnish. The inner mineral containing directional fine inclusions, when the mineral can occur when the color change colors, transparent minerals or cleavage fracture can sometimes cause the interference of light and appear like iridescent rainbow.
