Any array of electromagnetic visible light ordered according to its constituent wavelengths or colors, when the white light is dispersed by a prism or diffraction grating, ranging from about 750 to about 400 nm. The spectra can obtained by means of spectrometer. Spectra produced from a stone emitting radiation are known as emission spectra. If white light traversed a quasi translucent medium, selective absorption of certain wavelength or bands of wavelength takes place. This is known as an absorption spectrum. The rainbow colors in a continuous spectrum or Newtonian spectrum, in which all wavelengths, between certain limits are present. A number of sharp bright vertical lines caused by absorption of glowing vapors elements, is called line spectra. When the red flames from lithium and strontium salts are observed through a prism a different bright-line spectrum is given by each. It is caused by emission spectrum up of bright lines on a dark background is known as bright-line spectra. When a band containing a series of spaced lines, which are very close together so that can not be resolved. This is called band spectra. The emission and absorption spectra of gemstones are characteristic, which serve to identify the elements present in a material, while it exists in different positions of bright lines in the spectrum for different elements in any chemical compounds.